Remove Intel compiler support

include/linux/compiler-intel.h had no update in the past 3 years.

We often forget about the third C compiler to build the kernel.

For example, commit a0a12c3ed0 ("asm goto: eradicate CC_HAS_ASM_GOTO")
only mentioned GCC and Clang.

init/Kconfig defines CC_IS_GCC and CC_IS_CLANG but not CC_IS_ICC,
and nobody has reported any issue.

I guess the Intel Compiler support is broken, and nobody is caring
about it.

Harald Arnesen pointed out ICC (classic Intel C/C++ compiler) is
deprecated:

    $ icc -v
    icc: remark #10441: The Intel(R) C++ Compiler Classic (ICC) is
    deprecated and will be removed from product release in the second half
    of 2023. The Intel(R) oneAPI DPC++/C++ Compiler (ICX) is the recommended
    compiler moving forward. Please transition to use this compiler. Use
    '-diag-disable=10441' to disable this message.
    icc version 2021.7.0 (gcc version 12.1.0 compatibility)

Arnd Bergmann provided a link to the article, "Intel C/C++ compilers
complete adoption of LLVM".

lib/zstd/common/compiler.h and lib/zstd/compress/zstd_fast.c were kept
untouched for better sync with https://github.com/facebook/zstd

Link: https://www.intel.com/content/www/us/en/developer/articles/technical/adoption-of-llvm-complete-icx.html
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/compiler_attributes.h

@@ -64,16 +64,10 @@
  * compiler should see some alignment anyway, when the return value is
  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  *
- * Optional: not supported by icc
- *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  */
-#if __has_attribute(__assume_aligned__)
-# define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
-#else
-# define __assume_aligned(a, ...)
-#endif
+#define __assume_aligned(a, ...)        __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
 
 /*
  * Note the long name.
@@ -85,7 +79,6 @@
 /*
  * Optional: only supported since gcc >= 9
  * Optional: not supported by clang
- * Optional: not supported by icc
  *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  */
@@ -98,7 +91,6 @@
 /*
  * Optional: not supported by gcc
  * Optional: only supported since clang >= 14.0
- * Optional: not supported by icc
  *
  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
  */
@@ -122,7 +114,6 @@
 
 /*
  * Optional: not supported by clang
- * Optional: not supported by icc
  *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
  */
@@ -236,7 +227,6 @@
 /*
  * Optional: only supported since gcc >= 8
  * Optional: not supported by clang
- * Optional: not supported by icc
  *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
  */
@@ -267,7 +257,6 @@
 
 /*
  * Optional: not supported by gcc.
- * Optional: not supported by icc.
  *
  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
  */
@@ -287,7 +276,6 @@
  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
  *
  * Optional: not supported by gcc.
- * Optional: not supported by icc.
  *
  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
  */