xen/pv-on-hvm kexec: update xs_wire.h:xsd_sockmsg_type from xen-unstable

Update include/xen/interface/io/xs_wire.h from xen-unstable.
Now entries in xsd_sockmsg_type were added.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>