mfd: mc13xxx: Simplify probe() & remove()

This patch simplifies probe() and remove() functions by moving
some initialisation code out from the I2C/SPI init() and exit()
functions and into the core driver.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --cc drivers/mfd/mc13xxx-core.c
Simple merge

diff --cc drivers/mfd/mc13xxx-i2c.c
Simple merge

diff --cc drivers/mfd/mc13xxx-spi.c
Simple merge

diff --cc drivers/mfd/mc13xxx.h
Simple merge