[media] video: Kconfig: Select VIDEOBUF2_DMA_CONTIG for VIDEO_MX2

Fix the following build error:

LD      .tmp_vmlinux1
drivers/built-in.o: In function `mx2_camera_init_videobuf':
clkdev.c:(.text+0xcfaf4): undefined reference to `vb2_dma_contig_memops'
drivers/built-in.o: In function `mx2_camera_probe':
clkdev.c:(.devinit.text+0x5734): undefined reference to `vb2_dma_contig_init_ctx'
clkdev.c:(.devinit.text+0x5778): undefined reference to `vb2_dma_contig_cleanup_ctx'
drivers/built-in.o: In function `mx2_camera_remove':
clkdev.c:(.devexit.text+0x89c): undefined reference to `vb2_dma_contig_cleanup_ctx'

commit c6a41e32 ([media] media i.MX27 camera: migrate driver to videobuf2)
missed to select VIDEOBUF2_DMA_CONTIG in Kconfig.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/Kconfig

@@ -1109,7 +1109,7 @@ config VIDEO_MX2_HOSTSUPPORT
 config VIDEO_MX2
 	tristate "i.MX27/i.MX25 Camera Sensor Interface driver"
 	depends on VIDEO_DEV && SOC_CAMERA && (MACH_MX27 || ARCH_MX25)
-	select VIDEOBUF_DMA_CONTIG
+	select VIDEOBUF2_DMA_CONTIG
 	select VIDEO_MX2_HOSTSUPPORT
 	---help---
 	  This is a v4l2 driver for the i.MX27 and the i.MX25 Camera Sensor