ARM: stm32: Add additional ID register check for KSZ8851 presence

Currently the code sets eth1addr only if /ethernet1 alias exists in DT,
the node pointed to by the alias has "micrel,ks8851-mll" compatible
string, and the KSZ8851 CCR register read indicates programmed EEPROM
is not connected.

This is not sufficient to detect cases where the DT still contains the
KSZ8851 nodes, but the chip itself is not present. Extend the detection
to handle these cases.

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