media: staging: media: zoran: remove vidmem

The vidmem parameter is no longer necessary since we removed framebuffer
support.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>