ARM: dts: am437x-gp-evm: add LCD data

Add DT data for am437x-gp-evm's LCD panel.

Signed-off-by: Sathya Prakash M R <sathyap@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>