V4L/DVB: mfd: use reg_shift instead of regstep

Update for change in i2c-ocores.h which uses reg_shift to
specify the register offset shifts instead of regstep.

Signed-off-by: Jayachandran C <jayachandranc@netlogicmicro.com>
Acked-by: Richard Rojfors <richard.rojfors@pelagicore.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>