For DSI operation in videomode, DISPC logic levels for the signals HSYNC, VSYNC
and DE need to be specified to DSI via the fields VP_HSYNC_POL, VP_VSYNC_POL and
VP_DE_POL in DSI_CTRL registers.

This information is completely internal to DSS as logic levels for the above
signals hold no meaning on the DSI bus. Hence a DSI panel driver should be
totally oblivious of these fields.

Fix the logic levels/polarities in the DISPC and DSI registers to a default
value. This is done by overriding these fields in omap_video_timings struct
filled by the panel driver for DISPC, and use the equivalent default values
when programming DSI_CTRL registers. Also, remove the redundant polarity related
fields in omap_dss_dsi_videomode_data.
Signed-off-by: Archit Taneja <archit@ti.com>