[media] V4L2: OMAP: VOUT: dma map and unmap v4l2 buffers in qbuf and dqbuf

Add support to map the buffer using dma_map_single during qbuf which inturn
calls cache flush and unmap the same during dqbuf. This is done to prevent
the artifacts seen because of cache-coherency issues on OMAP4

Signed-off-by: Amber Jain <amber@ti.com>
Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>