staging: unisys: visorbus: device_changestate_responder add error handling

Pass the error returned from visorchannel_signalinsert up the stack
instead of just ignoring it.

Signed-off-by: David Kershner <david.kershner@unisys.com>
Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>