x86-32: Fix boot with CONFIG_X86_INVD_BUG

entry_32.S contained a hardcoded alternative instruction entry, and the
format changed in commit 59e97e4d ("x86: Make alternative
instruction pointers relative").

Replace the hardcoded entry with the altinstruction_entry macro.  This
fixes the 32-bit boot with CONFIG_X86_INVD_BUG=y.

Reported-and-tested-by: Arnaud Lacombe <lacombar@gmail.com>
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>