KVM: Portability: Move kvm_sregs and msr structures to <asm/kvm.h>

Move structures:
	kvm_sregs
	kvm_msr_entry
	kvm_msrs
	kvm_msr_list

from include/linux/kvm.h to include/asm-x86/kvm.h

Signed-off-by: Avi Kivity <avi@qumranet.com>