media: usbvision: Remove dead code

These codes are commented since v4.2-rc1. If there is no plan
to enable the #else part in future, these can be removed
forever.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>