V4L/DVB (3314): Fixed em28xx based system lockup

Fixed em28xx based system lockup, device needs to be initialized
before starting the isoc transfer otherwise the system will completly lock up.

Signed-off-by: Markus Rechberger <mrechberger@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>