ARM: dts: stm32: Keep MDIO bus in AF across suspend DH STM32MP13xx DHCOR DHSBC board

ARM: dts: stm32: Keep MDIO bus in AF across suspend DH STM32MP13xx DHCOR DHSBC board

The RTL8211F PHY gets confused when the MDIO bus lines get switched
to ANALOG during suspend/resume cycle. Keep the MDIO and MDC lines
in AF during suspend/resume to avoid confusing the PHY. The PHY can
be brought out of the confused state by restarting auto-negotiation
too, but that seems like an odd workaround and shouldn't be in the
PHY driver.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>