Staging: hv: remove vmbus_on_event_dpc()

Just call VmbusOnEvents() as that's all the function did, so we can
remove it.

Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>