[media] cx231xx: remove direct register PWR_CTL_EN modification that switches port3

The only remaining place that modifies the relevant bit is in function
cx231xx_set_Colibri_For_LowIF

Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>