In order get the ONIE EEPROM support and some mv88e6xxx related fixes,
move to 6.5.6, with the intention of upgrading again, to the next
longterm kernel, as soon as one becomes available.
Also, import patches from kkit-linux-6.5.y.
Our custom version has gone from being newer than Buildroot's default
to being older, so there is no reason for us override it anymore.
The kernel has become a bit more picky and will give nasty error
messages if a link's PHY connection is not explicitly defined, but
instead relies on implicit defaults. This was missing from the CPU
port of the CRB, so we supply a small patch to fix that.
