msm: mdss: Add support for dynamic mode switch on mdp3

Add support to dynamically switch between dsi video
mode and command mode for MDP3 driver. For a panel which
is configured in video mode and can support command mode,
it would be power efficient to dynamically switch to
command mode on need basis.

Change-Id: Iefb3c8aa453a8be4396fd04b65dcc462d01e26fb
Signed-off-by: Shivaraj Shetty <shivaraj@codeaurora.org>