Merge branch 'stmmac-next'

Giuseppe Cavallaro says:

====================
stmmac: rework and enhance the PCS support

The 3.xx and 4.xx synopsys gmacs have a very similar
PCS embedded module and they share almost the same registers;
for example:
  AN_Control, AN_Status, AN_Advertisement, AN_Link_Partner_Ability,
  AN_Expansion, TBI_Extended_Status.

Just the RGMII/SMII Control/Status register differs.

So these patches aim to reorganize and enhance the PCS support;
to do that, some small inline functions have been provided and
also some rework to the PCS ISR part has been done.

In the end, the SGMII for MAC2MAC connection has been introduced.

All patches have been built on top of net-next git and, as for
the previous version, not fully tested.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>