drm/tegra: dsi: Implement host transfers

Add support for sending MIPI DSI command packets from the host to a
peripheral. This is required for panels that need configuration before
they accept video data.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/tegra/dsi.c
Simple merge

diff --cc drivers/gpu/drm/tegra/dsi.h
Simple merge