mx6cuboxi: fixup dtb ethernet phy nodes before booting an OS

SoM revision 1.9 has replaced the ar8035 phy address 0 with an adin1300
at address 1. Because early SoMs had a hardware flaw, the ar8035 can
also appear at address 4 - making it a total of 3 phy nodes in the DTB.

To avoid confusing Linux with probe errors, fixup the dtb to only enable
the phy node that is detected at runtime.

Signed-off-by: Josua Mayer <josua@solid-run.com>