ARM: dts: omap3-igep0020: Remove duplicate uart2 pinmux

uart2 pinmux is already defined in omap3-igep0020-common.dtsi, remove
the duplicate node.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>