dt-bindings: net: remove un-implemented property

The `adi,disable-energy-detect` property was implemented in an initial
version of the `adin` driver series, but after a review it was discarded in
favor of implementing the ETHTOOL_PHY_EDPD phy-tunable option.

With the ETHTOOL_PHY_EDPD control, it's possible to disable/enable
Energy-Detect-Power-Down for the `adin` PHY, so this device-tree is not
needed.

Fixes: 76707813

 ("dt-bindings: net: add bindings for ADIN PHY driver")
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>