net: pse-pd: tps23881: Add support for power limit and measurement features

Expand PSE callbacks to support the newly introduced
pi_get/set_pw_limit() and pi_get_voltage() functions. These callbacks
allow for power limit configuration in the TPS23881 controller.

Additionally, the patch includes the pi_get_pw_class() the
pi_get_actual_pw(), and the pi_get_pw_limit_ranges') callbacks providing
more comprehensive PoE status reporting.

Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>