drm/msm/dp: remove extra wrappers and public functions

dp_bridge's functions are thin wrappers around the msm_dp_display_*
family. Squash dp_bridge callbacks into respective msm_dp_display
functions, removing the latter functions from public space.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/473858/
Link: https://lore.kernel.org/r/20220211224006.1797846-6-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>