ARM: dts: stm32: Do not set eth1addr if KS8851 has EEPROM

In case the KS8851 has external EEPROM attached to it, do not set
eth1addr at all. The network stack will read the MAC out of the
KS8851 and set eth1addr accordingly.

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