firmware: arm_scmi: Refactor scmi_wait_for_message_response

Refactor scmi_wait_for_message_response() to use a internal helper to
carry out its main duties; while doing that make it accept directly an
scmi_desc parameter to interact with the configured transport.

No functional change.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230118121426.492864-4-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>