regulator: bd718x7 fix regulator states at SUSPEND

The BD718(37/47/50) regulator enable states can be controlled
either by SW or by PMIC internal state machine. The bd718x7
driver has not supported leaving the regulators under HW state
machine control (except for cases where this is required to
avoid boot-up problems due to critical regulators being turned
OFF at reset when SNVS used as reset state).

On some systems this is undesirable as there now are setups where
mixture of SW and HW state machine controlled regulators is needed.

Specifically, some SoCs signal SUSPEND state change to PMIC via
STBY_REQ line. Now there are setups that expect certain regulators
then to be disabled (by PMIC state machine) while other regulators
should stay enabled (regardless of HW state => SW control required).

Add support for a new device-tree property
"rohm,no-regulator-enable-control" which can be used to leave
regulator(s) under HW state machine control.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/6ebba33dd08f2dcc9f1137bbff4d2dc905278a5a.1599029335.git.matti.vaittinen@fi.rohmeurope.comSigned-off-by: Mark Brown <broonie@kernel.org>