mfd: arizona: Fully support the use of MCLK1 as the 32kHz clock source

MCLK1 is not in the AoD power domain so if it is used as the 32kHz clock
source we need to hold a runtime PM reference to keep the device from going
into low power mode.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>