drm/msm/dsi: fuse dsi_pll_* code into dsi_phy_* code

Each phy version is tightly coupled with the corresponding PLL code,
there is no need to keep them separate. Fuse source files together in
order to simplify DSI code.

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/20210331105735.3690009-5-dmitry.baryshkov@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>