OMAP: DSS2: Support for UMSH-8173MD TFT panel

This patch adds support for Microtip Technologies' UMSH-8173MD 800x480
RGB TFT panel. Tested with an OMAP3 board.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
[tomi.valkeinen@ti.com: changed the panel name string]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>