[media] cx231xx: scan all four existing i2c busses instead of the 3 masters

The scanning itself just fails (as before this series) but now
the correct busses are scanned.

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>