regulator: dt-bindings: Convert Fairchild FAN53555 to DT schema

Convert the Fairchild FAN53555 and compatible variants binding to DT
schema format.

Add the undocumented 'vsel-gpios' property used to control the VSEL pin.

The example was missing 'reg', so add it.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230109004656.451231-1-robh@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>