regulator: s2mps11: update node parsing (allow -supply properties)

For the upcoming S2MPG10 and S2MPG11 support, we need to be able to
parse -supply properties in the PMIC's DT node.

This currently doesn't work, because the code here currently points the
regulator core at each individual regulator sub-node, and therefore the
regulator core is unable to find the -supply properties.

Update the code to simply let the regulator core handle all the parsing
by adding the ::of_match and ::regulators_node members to all existing
regulator descriptions, by adding ::of_parse_cb() to those
regulators which support the vendor-specific samsung,ext-control-gpios
to parse it (S2MPS14), and by dropping the explicit call to
of_regulator_match().

Configuring the PMIC to respect the external control GPIOs via
s2mps14_pmic_enable_ext_control() is left outside ::of_parse_cb()
because the regulator core ignores errors other than -EPROBE_DEFER from
that callback, while the code currently fails probe on register write
errors and I believe it should stay that way.

The driver can now avoid the devm_gpiod_unhinge() dance due to
simpler error handling of GPIO descriptor acquisition.

This change also has the advantage of reducing runtime memory
consumption by quite a bit as the driver doesn't need to allocate a
'struct of_regulator_match' and a 'struct gpio_desc *' for each
regulator for all PMICs as the regulator core does that. This saves
40+8 bytes on arm64 for each individual regulator on all supported
PMICs (even on non-S2MPS14 due to currently unnecessarily allocating
the extra memory unconditionally). With the upcoming S2MPG10 and
S2MPG11 support, this amounts to 1640+328 and 1120+224 bytes
respectively.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://patch.msgid.link/20260122-s2mpg1x-regulators-v7-14-3b1f9831fffd@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: andred