mfd: Support 88pm80x in 80x driver

88PM800 and 88PM805 are two discrete chips used for power management.
Hardware designer can use them together or only one of them according
to requirement.

88pm80x.c provides common i2c driver handling for both 800 and
805, such as i2c_driver init, regmap init, read/write api etc.

88pm800.c handles specifically for 800, such as chip init, irq
init/handle, mfd device register, including rtc, onkey, regulator(
to be add later) etc. besides that, 800 has three i2c device, one
regular i2c client, two other i2c dummy for gpadc and power purpose.

88pm805.c handles specifically for 805, such as chip init, irq
init/handle, mfd device register, including codec, headset/mic detect
etc.

the i2c operation of both 800 and 805 are via regmap, and 88pm80x-i2c
exported a group of r/w bulk r/w and bits set API for facility.

Signed-off-by: Qiao Zhou <zhouqiao@marvell.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>