net: phy: bcm7xxx: add an explicit version check for GPHY rev G0

GPHY revision G0 has its version rolled over to 0x10, introduce an
explicit check for that revision and invoke the proper workaround
function for it.

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