mfd: AB3100 alter default setting

This alters the default setting for AB3100_IMRB1 from 0xff to
0xbf. These registers are used for the yet unimplemented ADC
and this new setting will deactivate ADC Trigger 1.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>