drm/msm: Convert to drm_of_get_data_lanes_count

Convert driver to use this new helper to standardize
OF "data-lanes" parsing.

Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sean Paul <sean@poorly.run>
To: dri-devel@lists.freedesktop.org
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220524010522.528569-10-marex@denx.de