dri: Add config attributes for color channel shift

dri: Add config attributes for color channel shift

The existing mask attributes can only support up to 32 bpp. Introduce
per-channel SHIFT attributes that indicate how many bits, from lsb towards
msb, the bit field is offset. A shift of -1 will indicate that there is no
bit field set for the channel.

As old loaders will still be looking for masks, we set the masks to 0 for
any formats wider than 32 bpp.

Signed-off-by: Kevin Strasser <kevin.strasser@intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>