x86_64: fix section mismatch warning in hpet.c
x86_64: fix section mismatch warning in hpet.c

Fix following warnings:
WARNING: vmlinux.o(.text+0x945e): Section mismatch: reference to .init.text:__set_fixmap (between 'hpet_arch_init' and 'hpet_mask_rtc_irq_bit')
WARNING: vmlinux.o(.text+0x9474): Section mismatch: reference to .init.text:__set_fixmap (between 'hpet_arch_init' and 'hpet_mask_rtc_irq_bit')

hpet_arch_init is only used from __init context so mark it __init.

Signed-off-by: Sam Ravnborg <f16bed56189e249fe4ca8ed10a1ecae60e8ceac0@ravnborg.org>
Signed-off-by: Andi Kleen <0474aee45985f5ae829f53849df476200e876990@suse.de>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs