video: Add support for Armada XP LCD controller

This patch adds basic support for the LCD controller of the Marvell
Armada XP SoC.

An AXP based custom board port will be added later, to use this
driver to display a splash screen via the bmp command later.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>
[agust: rebased]
Signed-off-by: Anatolij Gustschin <agust@denx.de>