net: phy: mdio-gpio: Handle phy_ignore_ta_mask

Update mdiobb_read() to read whether the PHY has a broken turn-around,
and if it does, ignore it to make the read succeeed.

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