stmmac: support new GMAC4

This patch adds the whole GMAC4 support inside the
stmmac d.d. now able to use the new HW and some new features
i.e.: TSO.
It is missing the multi-queue and split Header support at this
stage.
This patch also updates the driver version and the stmmac.txt.

Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>