sh: add Video Output Unit and AK8813 video encoder support on ecovec

Ecovec uses the AK8813 video envoder similarly to the ms7724se platform with
the only difference, that on ecovec GPIOs are used for resetting and powering
up and down the chip.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>