drm/msm/dsi-staging: move mdp transfer time node to drm modes.

Each of the drm panel modes can set different mdp transfer time.
Move the node from panel dtsi to drm panel timing modes.

Change-Id: Ifd1a5fcf49420405531a8916c582ce96119d5457
Signed-off-by: Vara Reddy <varar@codeaurora.org>