of: mdio: Add a "broken-turn-around" property

Some Ethernet PHY devices/switches may not properly release the MDIO bus
during turn-around time, and fail to drive it low, which can be seen by
some controllers as a read failure, while the data clocked in is still
correct.

Add a boolean property "broken-turn-around" which is parsed by the
generic MDIO bus probing code and will set the corresponding bit in the
MDIO bus phy_ignore_ta_mask bitmask for MDIO bus drivers to utilize that
information.

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