mx31: add dma and fb devices

This adds the dma (ipu_dma) and fb devices for the mx31 for which drivers now are
available.

v2: merge the ipu and fb device in the same patch as suggested by Sascha

Signed-off-by: Valentin Longchamp <valentin.longchamp@epfl.ch>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>