ARM: stm32: Define I2C EEPROM bus and address on DHCOM

Define I2C EEPROM bus and address, so that the 'eeprom' command uses
the correct ones and does not generate the following error:
    eeprom_rw_block: Cannot find udev for a bus 0

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>