checkpatch: generalize xen handle matching in the list of types

checkpatch: generalize xen handle matching in the list of types

All the xen stable APIs define handle types of the form:

xen<subject of API>_handle

and some define additional handle types of the form:

xen<subject of API>_<purpose of handle>_handle

Examples of these are xenforeignmemory_handle and
xenforeignmemory_resource_handle.

Both of these types will be misparsed by checkpatch if they appear as the
first token in a line since, as types defined by an external library, they
do not conform to the QEMU CODING_STYLE, which suggests CamelCase.

A previous patch (5ac067a24a8) added xendevicemodel_handle to the list
of types. This patch changes that to xen\w+_handle such that it will
match all Xen stable API handles of the forms detailed above.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>