ANDROID: GKI: make VIDEOBUF2_DMA_CONTIG under GKI_HIDDEN_MEDIA_CONFIGS

it use vb2_dma_contig_memops as default mem_ops in csi driver
drivers/media/platform/mxc/capture/mx6s_capture.c still not upstream to linux community.
q->mem_ops = &vb2_dma_contig_memops;

mem_ops is need in videobuf2-core.c to operate dma buffer.
videobuf2-dma-contig.c is common code which have no hardware involved

Bug: 160195378
Signed-off-by: zhang sanshan <pete.zhang@nxp.com>
Change-Id: Ib084ff96bd4f92aa36f8abb8d4b62a0e9be62e6c