net: phy: dp83867: add workaround for incorrect RX_CTRL pin strap

net: phy: dp83867: add workaround for incorrect RX_CTRL pin strap

The data manual for DP83867IR/CR, SNLS484E[1], revised march 2017,
advises that strapping RX_DV/RX_CTRL pin in mode 1 and 2 is not
supported (see note below Table 5 (4-Level Strap Pins)).

It further advises that if a board has this pin strapped in mode 1 and
mode 2, then bit[7] of Configuration Register 4 (address 0x0031) must
be cleared to 0. This is to ensure proper operation of PHY.

Since it is not possible to detect in software if RX_DV/RX_CTRL pin is
incorrectly strapped, add a device-tree property to advertise this and
allow corrective action in software.
[1] http://www.ti.com/lit/ds/snls484e/snls484e.pdf

Signed-off-by: Murali Karicheri <[email protected]>
Reviewed-by: Hannes Schmelzer <[email protected]>
Acked-by: Joe Hershberger <[email protected]>
Tested-by: Siva Durga Prasad Paladugu <[email protected]>