net: fec: add fec_set_hw_mac_addr() helper function

In the current driver, the MAC address is set in both fec_restart() and
fec_set_mac_address(), so a generic helper function fec_set_hw_mac_addr()
is added to set the hardware MAC address to make the code more compact.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250711091639.1374411-4-wei.fang@nxp.com


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