V4L/DVB: OMAP_VOUT: fix: Replaced dma-sg with dma-contig

Actually OMAP doesn't support scatter-gather DMA for
Display subsystem but due to legacy coding it has been overlooked
till now.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Muralidharan Karicheri <mkaricheri@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>