staging: Import the BCM2835 MMAL-based V4L2 camera driver.

- Supports raw YUV capture, preview, JPEG and H264.
- Uses videobuf2 for data transfer, using dma_buf.
- Uses 3.6.10 timestamping
- Camera power based on use
- Uses immutable input mode on video encoder

This code comes from the Raspberry Pi kernel tree (rpi-4.9.y) as of
a15ba877dab4e61ea3fc7b006e2a73828b083c52.

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>