HSD #16018694129: net: stmmac: Enable XGMAC MDIO support for C22 devices with port id > 3 (#125)

commit 77f7389d7203fdac54eac97d095d2220c19f98cd from
https://github.com/altera-opensource/linux-socfpga.git



Enable XGMAC MDIO support for C22 devices with port id > 3.
XGMAC doesn't have any restrictions with port id > 3 for
C22 devices, it supports port id 0 to 31.

Signed-off-by: G Thomas, Rohan <rohan.g.thomas@intel.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>