net: phy: bcm7xxx: drop A0 revision workaround and fix B0 workaround

bcm7445_config_init() was working around non-production version of the
PHY HW block, so just remove it entirely.

bcm7xxx_28nm_afe_config_init() was running for all PHY revisions greater
than B0, but this workaround sequence is really specific to the B0 PHY
revision, so rename the function accordingly and update the GPHY macro
to use the generic config_init callback.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>