alpha: fix hard_smp_processor_id compile error

alpha: fix hard_smp_processor_id compile error

"Remove hardcoding of hard_smp_processor_id on UP systems",
2f4dfe206a2fc07099dfad77a8ea2f4b4ae2140f in Linus' tree, moved
the definition of hard_smp_processor_id linux/smp.h to asm/smp.h
for UP systems. This causes a regression on Alpha.

cc1: warnings being treated as errors
arch/alpha/kernel/setup.c: In function 'setup_arch':
arch/alpha/kernel/setup.c:506: warning: implicit declaration of function 'hard_smp_processor_id'
make[1]: *** [arch/alpha/kernel/setup.o] error 1
make: *** [arch/alpha/kernel] error 2

By including asm/smp.h non-conditionally in asm/mmu_context.h
the problem appears to be resolved.

Cc: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Simon Horman <horms@verge.net.au>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>