net: pse-pd: Kconfig: Add missing Regulator API dependency

The PSE (Power Sourcing Equipment) API now relies on the Regulator API.
However, the Regulator dependency was missing from Kconfig. This patch
adds the necessary dependency, resolving the issue of the missing
dependency and ensuring proper functionality of the PSE API.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404201020.mqX2IOu7-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202404200036.D8ap1Mf5-lkp@intel.com/


Fixes: d83e1376 ("net: pse-pd: Use regulator framework within PSE framework")
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://lore.kernel.org/r/20240423-fix_poe-v3-3-e50f32f5fa59@bootlin.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>