mfd: AB8500 register access via PRCMU I2C

This patch adds the choice of accessing the AB8500 registers
via prcmu I2C. Access either via SPI or I2C is supported.

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

diff --cc drivers/mfd/Kconfig
Simple merge

diff --cc drivers/mfd/Makefile
Simple merge

diff --cc drivers/mfd/ab8500-i2c.c
Simple merge

diff --cc drivers/mfd/ab8500-spi.c
Simple merge