drivers/media/video/pvrusb2: remove depends on CONFIG_EXPERIMENTAL

The CONFIG_EXPERIMENTAL config item has not carried much meaning for a
while now and is almost always enabled by default. As agreed during the
Linux kernel summit, remove it from any "depends on" lines in Kconfigs.

CC: Mike Isely <isely@pobox.com>
CC: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-By: Mike Isely <isely@pobox.com>