V4L/DVB (13287): ce6230 - saa7164-cmd: Fix wrong sizeof

Which is why I have always preferred sizeof(struct foo) over
sizeof(var).

Cc: Antti Palosaari <crope@iki.fi>
Acked-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>