net: dsa: remove get_mac_eee() method

The get_mac_eee() is no longer called by the core DSA code, nor are
there any implementations of this method. Remove it.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tUllU-007UzL-KV@rmk-PC.armlinux.org.uk


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