net: pse-pd: Add power limit check

Checking only the current limit is not sufficient. According to the
standard, voltage can reach up to 57V and current up to 1.92A, which
exceeds the power limit described in the standard (99.9W). Add a power
limit check to prevent this.

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>