net: stmmac: configure SerDes on mac_finish

SerDes will configure according to the provided interface mode after
finish a major reconfiguration of the interface mode.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Link: https://patch.msgid.link/20250227121522.1802832-5-yong.liang.choong@linux.intel.com


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