net: dsa: Move KS8995 to the DSA subsystem

By reading the datasheets for the KS8995 it is obvious that this
is a 100 Mbit DSA switch.

Let us start the refactoring by moving it to the DSA subsystem to
preserve development history.

Verified that the chip still probes the same after this patch
provided CONFIG_HAVE_NET_DSA, CONFIG_NET_DSA and CONFIG_DSA_KS8995
are selected.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250813-ks8995-to-dsa-v1-1-75c359ede3a5@linaro.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>