Fix following warning:
WARNING: vmlinux.o(.text+0x188ea): Section mismatch: reference to .init.text:__alloc_bootmem_core (between 'alloc_bootmem_high_node' and 'get_gate_vma')

alloc_bootmem_high_node() is only used from __init scope so declare it __init.
And in addition declare the weak variant __init too.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>