x86/alternatives: Make the x86nops[] symbol static

Sparse says:

  arch/x86/kernel/alternative.c:78:21: warning: symbol 'x86nops' was not declared. Should it be static?

Since x86nops[] is not used outside this file, Sparse is right and it can be made static.

Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210506190726.15575-1-paskripkin@gmail.com