x86: fix section mismatch warning in setup_64.c:nearby_node

nearby_node() were only used by __cpuinit amd_detect_cmp()
So annotating nearby_node() __cpuinit was the trivial fix.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>