dma-buf: add buffer mask to dma-buf container

dma-buf: add buffer mask to dma-buf container

Mask of dma-buf container is a bit-mask of buffers in the dma-buf
container. The bit order in the mask is the position of buffers in
the dma-buf container. LSB of the mask is the bit-mask of the buffer
0 in the dma-buf container.
The mask of a dma-buf container is zero on creation. This means that
all buffers in the dma-buf container are unmasked initially. Users
of dma-buf container can modify the mask of buffers later with the
following API functions/ioctl of dma-buf.
- dmabuf_container_set_mask()
- dmabuf_container_get_mask()
- DMA_BUF_IOCTL_CONTAINER_SET_MASK
- DMA_BUF_IOCTL_CONTAINER_GET_MASK

The mask of dma-buf container is not used by dma-buf container itself.
How to use the mask is entirely rely on the users. Users can configure
the activation information of buffers of a dma-buf container. Others
may use the mask to indicate buffers with special information.

Change-Id: I2cc7d68812c060ed4fabb50da89271d52ad01ddc
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>