KVM: VMX: move ASM_VMX_* definitions from asm/kvm_host.h to asm/vmx.h

Those definitions will be used by code outside KVM, so move it outside
of a KVM-specific source file.

Those definitions are used only on kvm/vmx.c, that already includes
asm/vmx.h, so they can be moved safely.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>