drm/dsi: Implement DCS set_{column,page}_address commands

Provide small convenience wrappers to set the column and page extents of
the frame memory accessed by the host processors.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/drm_mipi_dsi.c
Simple merge

diff --cc include/drm/drm_mipi_dsi.h
Simple merge