drm/msm: add DSI support for sc7180

Add support for v2.4.1 DSI block in the sc7180 SoC.

Changes in v1:
	-Modify commit text to indicate DSI version and SOC detail(Jeffrey Hugo).
	-Splitting visionox panel driver code out into a
	 different patch(set), since panel drivers are merged into
	 drm-next via a different tree(Rob Clark).
Changes in v2:
	-Update commit text accordingly(Matthias Kaehlcke).

Signed-off-by: Harigovindan P <harigovi@codeaurora.org>
[cleanup subject / commit message]
Signed-off-by: Rob Clark <robdclark@chromium.org>