KVM: Add ifdef in irqchip struct for x86 only structures

This patch fixes a small issue where sturctures:
	kvm_pic_state
	kvm_ioapic_state

are defined inside x86 specific code and may or may not
be defined in anyway for other architectures. The problem
caused is one cannot compile userspace apps (ex. libkvm)
for other archs since a size cannot be determined for these
structures.

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>