media: uvcvideo: Remove format descriptions

The V4L2 core overwrites format descriptions in v4l_fill_fmtdesc(),
there's no need to manually set the descriptions in the driver. This
prepares for removal of the format descriptions from the uvc_fmts table.

Unlike V4L2, UVC makes a distinction between the SD-DV, SDL-DV and HD-DV
formats. It also indicates whether the DV format uses 50Hz or 60Hz. This
information is parsed by the driver to construct a format name string
that is printed in a debug message, but serves no other purpose as V4L2
has a single V4L2_PIX_FMT_DV pixel format that covers all those cases.

As the information is available in the UVC descriptors, and thus
accessible to users with lsusb if they really care, don't log it in a
debug message and drop the format name string to simplify the code.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Michael Grzeschik <m.grzeschik@pengutronix.de>