media: videodev2.h: add new capabilities for buffer types

VIDIOC_REQBUFS and VIDIOC_CREATE_BUFFERS will return capabilities
telling userspace what the given buffer type is capable of.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>