The miii_nway_restart() causes a PHY link change activity and
ax88772_link_reset will be called. link_reset will set
AX_CMD_WRITE_MEDIUM_MODE register correctly.
The asix_write_medium_mode in reset() fills in a default value to the register
which may be different from the negotiation result. So do this first.
Ignore the ret value since it's ignored in XXX_link_reset() functions.