[media] nuvoton-cir: use request_muxed_region for accessing EFM registers

The two EFM ioports are accessed by drivers for other parts of the Nuvoton
Super-IO chips too. Therefore access to these ioports needs to be
protected by using request_muxed_region (like it's implemented e.g. in
hwmon/nct6775 already).

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>