V4L/DVB (4622): Copy-paste bug in videodev.c

This patch fixes a copy-paste bug in videodev.c where the vidioc_qbuf()
function gets called for the dqbuf ioctl.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>