ARM: shmobile: dts: Add common file for AA104XD12 panel

The Mitsubishi AA104XD12 panel is commonly used with the Marzen, Lager
and Koelsch boards. Create a .dtsi file that describe the panel and its
connection to the board.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>