regulator: wm8994: Pass descriptor instead of GPIO number

regulator: wm8994: Pass descriptor instead of GPIO number

Instead of passing a global GPIO number for the enable GPIO, pass
a descriptor looked up from the device tree node or the board file
decriptor table for the regulator.

There is a single board file passing the GPIOs for LDO1 and LDO2
through platform data, so augment this to pass descriptors
associated with the i2c device as well.

The special GPIO enable DT property for the enable GPIO is
nonstandard but this was accomodated in
commit ae8c61793c551b19e161636b897ec6cf40500e1c
"gpio: of: Support regulator nonstandard GPIO properties".

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>