Marvell's 88PM886 PMIC has a so-called General Purpose ADC used for
monitoring various system voltages and temperatures. Add the relevant
register definitions to the MFD header and a driver for the ADC.
Acked-by: Karel Balej <balejk@matfyz.cz> # for the PMIC
Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>