[media] sh-vou: clarify videobuf2 dependency

The sh-vou driver has been converted from videobuf to videobuf2, but
the Kconfig file still lists VIDEOBUF_DMA_CONTIG as a dependency.
Consequently we can build the driver without VIDEOBUF2_DMA_CONTIG
and get a link error:

drivers/built-in.o: In function `sh_vou_probe':
vf610-ocotp.c:(.text+0x2dbf5c): undefined reference to `vb2_dma_contig_init_ctx'
vf610-ocotp.c:(.text+0x2dc0b4): undefined reference to `vb2_dma_contig_cleanup_ctx'
vf610-ocotp.c:(.text+0x2dc144): undefined reference to `vb2_dma_contig_memops'
drivers/built-in.o: In function `sh_vou_remove':
vf610-ocotp.c:(.text+0x2dc190): undefined reference to `vb2_dma_contig_cleanup_ctx'

This changes the dependency to VIDEOBUF2_DMA_CONTIG instead.

Fixes: 57af3ad5 ("[media] sh-vou: convert to vb2")

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