net: bcmgenet: Software reset EPHY after power on

The EPHY on GENET v1->v3 is extremely finicky, and will show occasional
failures based on the timing and reset sequence, ranging from duplicate
packets, to extremely high latencies.

Perform an additional software reset, and re-configuration to make sure it is
in a consistent and working state.

Fixes: 6ac3ce82 ("net: bcmgenet: Remove excessive PHY reset")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>