Use new display drivers for AM3517EVM board.

The new OMAP display drivers were merged for 3.11, and we can now change
the board files to use the new ones and phase out the old ones.

Note: the management of LCD GPIOs is unclear. They were originally muxed
as inputs, and LCD_PANEL_PWR was labelled as "dvi enable".
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>