net: phy: bcm7xxx: define soft_reset for 40nm EPHY

The internal 40nm EPHYs use a "Workaround for putting the PHY in
IDDQ mode." These PHYs require a soft reset to restore functionality
after they are powered back up.

This commit defines the soft_reset function to use genphy_soft_reset
during phy_init_hw to accommodate this.

Fixes: 6e2d85ec ("net: phy: Stop with excessive soft reset")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>