ARM: dts: imx6: skov: provide panel support for lt2 variants

Add support for the Logic Technologies LTTD800x480 L2RT 7" 800x480 TFT
Resistive Touch Module.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>