x86: Remove __FORCE_ORDER workaround

x86: Remove __FORCE_ORDER workaround

GCC PR82602 that caused invalid scheduling of volatile asms:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82602

was fixed for gcc-8.1.0, the current minimum version of the
compiler required to compile the kernel.

Remove workaround that prevented invalid scheduling for
compilers, affected by PR82602.

There were no differences between old and new kernel object file
when compiled for x86_64 defconfig with gcc-8.1.0.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250407112316.378347-1-ubizjak@gmail.com