[media] platform: pxa_camera: add VIDEO_V4L2 dependency

[media] platform: pxa_camera: add VIDEO_V4L2 dependency

Moving the pxa_camera driver from soc_camera lots the implied
VIDEO_V4L2 Kconfig dependency, and building the driver without
V4L2 results in a kernel that cannot link:

drivers/media/platform/pxa_camera.o: In function `pxa_camera_remove':
pxa_camera.c:(.text.pxa_camera_remove+0x10): undefined reference to `v4l2_clk_unregister'
pxa_camera.c:(.text.pxa_camera_remove+0x18): undefined reference to `v4l2_device_unregister'
drivers/media/platform/pxa_camera.o: In function `pxa_camera_probe':
pxa_camera.c:(.text.pxa_camera_probe+0x458): undefined reference to `v4l2_of_parse_endpoint'
drivers/media/v4l2-core/videobuf2-core.o: In function `__enqueue_in_driver':
drivers/media/v4l2-core/videobuf2-core.o: In function `vb2_core_streamon':
videobuf2-core.c:(.text.vb2_core_streamon+0x1b4): undefined reference to `v4l_vb2q_enable_media_source'
drivers/media/v4l2-core/videobuf2-v4l2.o: In function `vb2_ioctl_reqbufs':
videobuf2-v4l2.c:(.text.vb2_ioctl_reqbufs+0xc): undefined reference to `video_devdata'

This adds back an explicit dependency.

Fixes: 3050b9985024 ("[media] media: platform: pxa_camera: move pxa_camera out of soc_camera")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>