disp: msm: add new mode to notify when there is a fps change

Add a new mode DRM_PANEL_BLANK_FPS_CHANGE whenever there is
a change in fps and the power mode remains the same.
This will avoid unnecessary resume operations in touch driver.

Change-Id: Id3d5884ba862c864782636360e3832854464bf65
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>