The Always On Subsystem (AOSS) Qualcomm Messaging Protocol (QMP) driver
is used to communicate with the AOSS for certain side-channel requests,
that are not available through the RPMh interface.

The communication is a very simple synchronous mechanism of messages
being written in message RAM and a doorbell in the AOSS is rung. As the
AOSS has processed the message length is cleared and an interrupt is
fired by the AOSS as acknowledgment.

The driver exposes the QDSS clock as a clock and the low-power state
associated with the remoteprocs in the system as a set of power-domains.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>