ARM: mx3/mx31moboard: properly allocate memory for mx3-camera

It's not allowed to create an alias of system RAM for DMA.  So the memory
used must not be allocated using dma_alloc_coherent but has to be reserved
before using memblock routines.

There is no need to memzero the buffer because dma_alloc_coherent zeros
the memory for us.

LAKML-Reference: 1299271882-2130-4-git-send-email-u.kleine-koenig@pengutronix.de
Tested-by: Philippe Retornaz <philippe.retornaz@epfl.ch>
Acked-by: Philippe Retornaz <philippe.retornaz@epfl.ch>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>