media: media/usb: don't set description in ENUM_FMT

The V4L2 core sets the description for the driver in order to ensure
consistent naming.

So drop the strscpy of the description in drivers. Also remove any
description strings in driver-internal structures since those are
no longer needed.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>