x86: unify irqinit_{32,64}.c into irqinit.c

Impact: cleanup

Reviewed-by Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

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

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

diff --cc arch/x86/kernel/irqinit_64.c
Simple merge