kernel: move mv88e6xxx fix to generic backports

kernel: move mv88e6xxx fix to generic backports

The backports introduced in commit d40756563c46 ("kernel: backport
phylink changes from mainline Linux") broke the mv88e6xxx DSA driver.
A backport to fix this was added to the kirkwood target, but as it is
used in multiple targets, and there's a kmod package for it, the fix
should be in generic backports.

This fixes the switch on the WatchGuard Firebox M300 when running the
6.1 testing kernel.

There is no need to backport the fix for the 6.6 kernel, as it was
included in 6.6.5.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>