firmware: arm_scmi: Fix deferred_tx_wq release on error paths

firmware: arm_scmi: Fix deferred_tx_wq release on error paths

Use devres to allocate the dedicated deferred_tx_wq polling workqueue so
as to automatically trigger the proper resource release on error path.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 5a3b7185c47c ("firmware: arm_scmi: Add atomic mode support to virtio transport")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221028140833.280091-6-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>