staging: drm/imx: Add i.MX IPUv3 crtc support

This adds a i.MX51/53/6 IPU (Image Processing Unit) KMS driver. The
driver has been tested on the i.MX51 babbage board, the i.MX53 LOCO
board and the i.MX6q sabrelite board in different clone mode and dual
head setups.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>