OMAP: DSS2: Add generic DPI panel display driver

Generic DPI panel driver includes the driver and 4 similar panel configurations. It
will match the panel name which is passed from platform data and setup the
right configurations.

With generic DPI panel driver, we can remove those 4 duplicated panel display
drivers. In the future, it is simple for us just add new panel configuration
date in panel-generic-dpi.c to support new display panel.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>