firmware: arm_scmi: rename get_transition_latency and add_opps_to_device

firmware: arm_scmi: rename get_transition_latency and add_opps_to_device

Most of the scmi code follows the suggestion from Greg KH on a totally
different thread[0] to have the subsystem name first, followed by the
noun and finally the verb with couple of these exceptions.

This patch fixes them so that all the functions names are aligned to
that practice.

[0] https://www.spinics.net/lists/arm-kernel/msg583673.html

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>