x86: process_32.c declare cpu_number before they get used

Moved DECLARE_PER_CPU(int, cpu_number) from CONFIG_X86_32_SMP to CONFIG_X86_32
because cpu_number is required for both.
And include asm/smp.h in process_32.c

Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>