soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches

Add changes to invoke rpmh flush() from CPU PM notification.
This is done when the last the cpu is entering deep CPU idle
states and controller is not busy.

Controllers that have 'HW solver' mode like display RSC do not need
to register for CPU PM notification. They may be in autonomous mode
executing low power mode and do not require rpmh_flush() to happen
from CPU PM notification.

Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1586703004-13674-5-git-send-email-mkshah@codeaurora.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>