Add enable/disable support for switch regulators on pfuze100.

Based on commit 5fe156f1 ("regulator: pfuze100: add enable/disable for
switch") which is reverted due to boot regressions by commit 464a5686
("regulator: Revert "regulator: pfuze100: add enable/disable for switch"").
Disabling the switch regulators will only be done if the user specifies
"fsl,pfuze-support-disable-sw" in its device tree to keep backward
compatibility with current dtb's [1].

[1] https://patchwork.kernel.org/patch/10490381/Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>