regulator: Support ROHM BD9576MUF and BD9573MUF

Add initial support for ROHM BD9576MUF and BD9573MUF PMICs regulators.
These PMICs are mainly used to power the R-Car series processors.

The BD9576 includes some functional-safety features which are not
present on BD9573.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/78baea1d7922506827ca717e277e4e6b391bbb78.1600329307.git.matti.vaittinen@fi.rohmeurope.com
Signed-off-by: Mark Brown <broonie@kernel.org>