hw/xen: Subsume xen_be_register_common() into xen_be_init()

Every caller of xen_be_init() checks and exits on error, then calls
xen_be_register_common(). Just make xen_be_init() abort for itself and
return void, and register the common devices too.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
4 files changed