pse-core: Conditionally set current limit during PI regulator registration

Fix an issue where `devm_regulator_register()` would fail for PSE
controllers that do not support current limit control, such as simple
GPIO-based controllers like the podl-pse-regulator. The
`REGULATOR_CHANGE_CURRENT` flag and `max_uA` constraint are now
conditionally set only if the `pi_set_current_limit` operation is
supported. This change prevents the regulator registration routine from
attempting to call `pse_pi_set_current_limit()`, which would return
`-EOPNOTSUPP` and cause the registration to fail.

Fixes: 4a83abce ("net: pse-pd: Add new power limit get and set c33 features")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Tested-by: Kyle Swenson <kyle.swenson@est.tech>
Link: https://patch.msgid.link/20240813073719.2304633-1-o.rempel@pengutronix.de


Signed-off-by: Paolo Abeni <pabeni@redhat.com>