net: dsa: fix older DSA drivers using phylink

Older DSA drivers that do not provide an dsa_ops adjust_link method end
up using phylink. Unfortunately, a recent phylink change that requires
its supported_interfaces bitmap to be filled breaks these drivers
because the bitmap remains empty.

Rather than fixing each driver individually, fix it in the core code so
we have a sensible set of defaults.

Reported-by: Sergei Antonov <saproj@gmail.com>
Fixes: de5c9bf4

 ("net: phylink: require supported_interfaces to be filled")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com> # dsa_loop
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/E1qOflM-001AEz-D3@rmk-PC.armlinux.org.uk


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