drm/msm/dsi: add continuous clock support for 7nm PHY

Unlike previous generations, 7nm PHYs are required to collaborate with
the host for continuos clock mode. Add changes neccessary to enable
continuous clock mode in the 7nm DSI PHYs.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210805170817.3337665-1-dmitry.baryshkov@linaro.org


[Fix merge conflict, and $description typo]
Signed-off-by: Rob Clark <robdclark@chromium.org>