Revert "kbuild: avoid static_assert for genksyms"

Revert "kbuild: avoid static_assert for genksyms"

This reverts commit d061a4ca35a1b31d4a1c5d6d8f428c7905bdb8b8.

Macro Elver had sent a fix proper fix earlier, and also pointed out
corner cases:
 "I guess what you propose is simpler, but might still have corner cases
  where we still get warnings. In particular, if some file (for whatever
  reason) does not include build_bug.h and uses a raw _Static_assert(),
  then we still get warnings. E.g. I see 1 user of raw _Static_assert()
  (drivers/gpu/drm/amd/amdgpu/amdgv_sriovmsg.h )."

I believe the raw use of _Static_assert() should be allowed, so this
should be fixed in genksyms.

Even after commit d061a4ca35a1 ("kbuild: avoid static_assert for
genksyms"), I confirmed the following test code emits the warning.

  ---------------->8----------------
  #include <linux/export.h>

  _Static_assert((1 ?: 0), "");

  void foo(void) { }
  EXPORT_SYMBOL(foo);
  ---------------->8----------------

  WARNING: modpost: EXPORT symbol "foo" [vmlinux] version generation failed, symbol will not be versioned.

Now that commit 869b91992bce ("genksyms: Ignore module scoped
_Static_assert()") fixed this issue properly, the workaround should
be reverted.

Link: https://lkml.org/lkml/2020/12/10/845
Link: https://lkml.kernel.org/r/20201219183911.181442-1-masahiroy@kernel.org
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>