dt-bindings: net: pse-pd: microchip,pd692x0: Add manager regulator supply

dt-bindings: net: pse-pd: microchip,pd692x0: Add manager regulator supply

Adds the regulator supply parameter of the managers.
Update also the example as the regulator supply of the PSE PIs
should be the managers itself and not an external regulator.

Signed-off-by: Kory Maincent (Dent Project) <kory.maincent@bootlin.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250617-feature_poe_port_prio-v14-11-78a1a645e2ee@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>