drm/msm/dp: switch to struct drm_edid

Prefer the struct drm_edid based functions for reading the EDID and
updating the connector.

Simplify the flow by updating the EDID property when the EDID is read
instead of at .get_modes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/593976/
Link: https://lore.kernel.org/r/93d6c446ed4831dadfb4a77635a67cf5f27e19ff.1715691257.git.jani.nikula@intel.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>