i.MX31: framebuffer driver

This is a framebuffer driver for i.MX31 SoCs. It only supports synchronous
displays, vertical panning supported, no overlay support.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>