firmware: arm_scmi: Make smc support sync_cmds_completed_on_ret

Enable sync_cmds_completed_on_ret in the SMC transport descriptor and
remove SMC specific .poll_done callback support since polling is bypassed
when sync_cmds_completed_on_ret is set.

Link: https://lore.kernel.org/r/20211220195646.44498-5-cristian.marussi@arm.com


Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>