net: stmmac: configure FPE via ethtool-mm

Implement ethtool --show-mm and --set-mm callbacks.

NIC up/down, link up/down, suspend/resume, kselftest-ethtool_mm,
all tested okay.

Signed-off-by: Furong Xu <0x1207@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/06ed409314fe0ee37b78b800922f2c0cce762532.1725631883.git.0x1207@gmail.com


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