V4L/DVB (3906): ZC0301 driver updates

This is a patch fixing a small bug in zc0301_start_transfer()
introduced in the ZC0301 driver v1.04.

Signed-off-by: Luca Risolia <luca.risolia@studio.unibo.it>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>