media: v4l2-ctrls: add support for area type logging

A 'case V4L2_CTRL_TYPE_AREA' was missing in v4l2_ctrl_type_op_log,
which led to an 'unknown type' message in the kernel log.

Add support for controls of this type.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>