ARM: dts: stm32: Describe M24256E write-lockable page in DH STM32MP13xx DHCOR SoM DT

The STM32MP13xx DHCOR SoM is populated with M24256E EEPROM which has
Additional Write lockable page at separate I2C address. Describe the
page in DT to make it available.

Note that the WLP page on this device is hardware write-protected by
R37 which pulls the nWC signal high to VDD_3V3_1V8 power rail.

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