staging: unisys: visorbus: add error handling for parahotplug_request_kickoff

The function kobject_uevent_env returns an error we shouldn't just drop it
on the floor but we should report it back to the caller. Since it now
returns an error, need to add proper error handling to
parahotplug_process_message.

Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Reviewed-by: Tim Sell <timothy.sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>