net: phy: add qca8081 soft_reset and enable master/slave seed

qca8081 phy is a single port phy, configure
phy the lower seed value to make it linked as slave
mode easier.

Signed-off-by: Luo Jie <luoj@codeaurora.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>