kernel: netdevices: fold mv88e6xxx into one package

kernel: netdevices: fold mv88e6xxx into one package

This was the first DSA packaged, and the tagger was made into
a separate package. This is too complicated: the mv88e6xxx
is the only module using this tagger after all, fold the module
for the DSA hardware and the driver for the tagger into a
single package and let modprobe do its job of probing the
tagger for the driver.

Tested on the BMIPS Inteno XG6846.

Link: https://patchwork.ozlabs.org/project/openwrt/patch/20250110-mv88e6xxx-single-package-v1-1-223ad7fb312e@linaro.org/
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>