[media] V4L2: omap_vout: Remove GFP_DMA allocation as ZONE_DMA is not configured on OMAP

Remove GFP_DMA from the __get_free_pages() call from omap_vout as ZONE_DMA
is not configured on OMAP. Earlier the page allocator used to return a page
from ZONE_NORMAL even when GFP_DMA is passed and CONFIG_ZONE_DMA is disabled.
As a result of commit a197b59a, page allocator
returns null in such a scenario with a warning emitted to kernel log.

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>