mfd: Provide platform data for WM831x GPIO configuration

Allow the GPIO mode of WM831x devices to be configured using platform data.
Users may provide a table of GPIO register values in gpio_defaults[]. In
order to allow 0 to be set explicitly out of range values are accepted and
masked off, with a WM831X_GPIO_CONFIGURE define provided to set an out of
range value.

This can be used to configure higher numbered GPIOs or override values set
in OTP for GPIOs configured using OTP.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>