drm/msm/dsi_phy_28nm: Replace parent names with clk_hw pointers

parent_hw pointers are easier to manage and cheaper to use than
repeatedly formatting the parent name and subsequently leaving the clk
framework to perform lookups based on that name.

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/491925/
Link: https://lore.kernel.org/r/20220629225331.357308-9-marijn.suijten@somainline.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>