net: stmmac: move stmmac_fpe_cfg to stmmac_priv data

By moving the fpe_cfg field to the stmmac_priv data, stmmac_fpe_cfg
becomes platform-data eventually, instead of a run-time config.

Suggested-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Furong Xu <0x1207@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://patch.msgid.link/d9b3d7ecb308c5e39778a4c8ae9df288a2754379.1725631883.git.0x1207@gmail.com


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