y2038: Remove newstat family from default syscall set

We have four generations of stat() syscalls:
- the oldstat syscalls that are only used on the older architectures
- the newstat family that is used on all 64-bit architectures but
  lacked support for large files on 32-bit architectures.
- the stat64 family that is used mostly on 32-bit architectures to
  replace newstat
- statx() to replace all of the above, adding 64-bit timestamps among
  other things.

We already compile stat64 only on those architectures that need it,
but newstat is always built, including on those that don't reference
it. This adds a new __ARCH_WANT_NEW_STAT symbol along the lines of
__ARCH_WANT_OLD_STAT and __ARCH_WANT_STAT64 to control compilation of
newstat. All architectures that need it use an explict define, the
others now get a little bit smaller, and future architecture (including
64-bit targets) won't ever see it.

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

fs/stat.c

@@ -280,6 +280,8 @@ SYSCALL_DEFINE2(fstat, unsigned int, fd, struct __old_kernel_stat __user *, stat
 
 #endif /* __ARCH_WANT_OLD_STAT */
 
+#ifdef __ARCH_WANT_NEW_STAT
+
 #if BITS_PER_LONG == 32
 #  define choose_32_64(a,b) a
 #else
@@ -378,6 +380,7 @@ SYSCALL_DEFINE2(newfstat, unsigned int, fd, struct stat __user *, statbuf)
 
 	return error;
 }
+#endif
 
 static int do_readlinkat(int dfd, const char __user *pathname,
 			 char __user *buf, int bufsiz)