[media] V4L: mx3_camera: select VIDEOBUF2_DMA_CONTIG instead of VIDEOBUF_DMA_CONTIG

Since commit

	379fa5d3 ([media] V4L: mx3_camera: convert to videobuf2)

mx3_camera uses videobuf2, but that commit didn't upgrade the select
resulting in the following build failure:

	drivers/built-in.o: In function `mx3_camera_init_videobuf':
	clkdev.c:(.text+0x86580): undefined reference to `vb2_dma_contig_memops'
	drivers/built-in.o: In function `mx3_camera_probe':
	clkdev.c:(.devinit.text+0x3548): undefined reference to `vb2_dma_contig_init_ctx'
	clkdev.c:(.devinit.text+0x3578): undefined reference to `vb2_dma_contig_cleanup_ctx'
	drivers/built-in.o: In function `mx3_camera_remove':
	clkdev.c:(.devexit.text+0x674): undefined reference to `vb2_dma_contig_cleanup_ctx'
	make[2]: *** [.tmp_vmlinux1] Error 1
	make[1]: *** [sub-make] Error 2
	make: *** [all] Error 2

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>