ARM: dts: ls1021a: Specify TBIPA register address

The current (mildly evil) fsl_pq_mdio code uses an undocumented shadow of
the TBIPA register on LS1021A, which happens to be read-only.
Changing TBI PHY address therefore does not work on LS1021A.

The real (and documented) address of the TBIPA registere lies in the eTSEC
block and not in MDIO/MII, which is read/write, so using that fixes
the problem.

Signed-off-by: Esben Haabendal <eha@deif.com>
Signed-off-by: David S. Miller <davem@davemloft.net>