[media] v4l2-ioctl: set V4L2_CAP_EXT_PIX_FORMAT for device_caps

V4L2_CAP_EXT_PIX_FORMAT is set for capabilities, but it needs to be set for
device_caps as well: device_caps should report all caps relevant to the
device node, and this is one of them.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>