x86: fix section mismatch in srat_64.c:reserve_hotadd

reserve_hotadd() are only used by __init acpi_numa_memory_affinity_init().
Annotate reserve_hotadd() with __init is 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>