ARM: dts: stm32: Disable LAN8710 EDPD on DHCOM

The LAN8710 Energy Detect Power Down (EDPD) functionality might cause
unreliable cable detection. There are multiple accounts of this in the
SMSC PHY driver patches which attempted to make EDPD reliable, however
it seems there is always some sort of corner case left. Unfortunatelly,
there is no errata documented which would confirm this to be a silicon
bug on the LAN87xx series of PHYs (LAN8700, LAN8710, LAN8720 at least).

Disable EDPD on the DHCOM SoM, just like multiple other boards already
do as well, to make the cable detection reliable.

Fixes: 34e0c784 ("ARM: dts: stm32: Add DH Electronics DHCOM STM32MP1 SoM and PDK2 board")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>