drm/msm/dsi: push provided clocks handling into a generic code

All MSM DSI PHYs provide two clocks: byte and pixel ones.
Register/unregister provided clocks from the generic place, removing
boilerplate code from all MSM DSI PHY drivers.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Tested-by: Stephen Boyd <swboyd@chromium.org> # on sc7180 lazor
Link: https://lore.kernel.org/r/20210331105735.3690009-11-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>