x86, apic: separate 32-bit setup functionality out of apic_32.c

Impact: build fix, cleanup

A couple of arch setup callbacks were mistakenly in apic_32.c, breaking
the build.

Also simplify the code a bit.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --cc arch/x86/kernel/Makefile
Simple merge

diff --cc arch/x86/kernel/apic/Makefile
Simple merge

diff --cc arch/x86/kernel/apic/probe_32.c
Simple merge

diff --cc arch/x86/kernel/setup.c
Simple merge