mfd: arizona: Simplify adding subdevices

The code was using a switch on the code type to execute
one of several mfd_add_devices() calls. We're already
switching on the code type earlier in the function to
select the correct patch function so we can roll selection
of the mfd device table into the same switch.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>