evtchn: simplify sending of notifications

evtchn: simplify sending of notifications

The trivial wrapper evtchn_set_pending() is pretty pointless, as it
only serves to invoke another wrapper evtchn_port_set_pending(). In
turn, the latter is kind of inconsistent with its siblings in that is
takes a struct vcpu * rather than a struct domain * - adjusting this
allows for more efficient code in the majority of cases.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>