[media] dt3155: add GFP_DMA32 flag to vb2 queue

Ensure that buffers are allocated from the DMA32 zone since this
device only handles 32 bit DMA addresses.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>