net: dsa: mv88e6xxx: Fix validation of built-in PHYs on 6095/6097

net: dsa: mv88e6xxx: Fix validation of built-in PHYs on 6095/6097

These chips have 8 built-in FE PHYs and 3 SERDES interfaces that can
run at 1G. With the blamed commit, the built-in PHYs could no longer
be connected to, using an MII PHY interface mode.

Create a separate .phylink_get_caps callback for these chips, which
takes the FE/GE split into consideration.

Fixes: 2ee84cfefb1e ("net: dsa: mv88e6xxx: convert to phylink_generic_validate()")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20220213185154.3262207-1-tobias@waldekranz.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>