Use transport specific transmission timeout (max_rx_timeout_ms) also for
polling transactions.

Initially when polling mode was added, it was intended to be used only
in scheduler context and hence the choice of 100us for the polling timeout.
However the only user for that was dropped for other SCMI concurrency
issues, so it shouldn't cause any issue to increase this timeout value now.

Link: https://lore.kernel.org/r/20211129191156.29322-3-cristian.marussi@arm.comReviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
[sudeep.holla: Updated commit message with historical facts about 100us timeout]
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>