net: dsa: provide implementation of .support_eee()

commit 99379f58 upstream.

Provide a trivial implementation for the .support_eee() method which
switch drivers can use to simply indicate that they support EEE on
all their user ports.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/E1tL149-006cZJ-JJ@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Harshit: Resolve contextual conflicts due to missing commit:
  53977061 ("net: dsa: remove obsolete phylink dsa_switch operations")
  and commit: ecb595eb ("net: dsa: remove
  dsa_port_phylink_mac_select_pcs()") in 6.12.y ]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>