stmmac: add MMC support exported via ethtool (v3)

This patch adds the MMC management counters support.
MMC module is an extension of the register address
space and all the hardware counters can be accessed
via ethtoo -S ethX.

Note that, the MMC interrupts remain masked and the logic
to handle this kind of interrupt will be added later (if
actually useful).

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 290b97a..e08fee8 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -29,6 +29,7 @@
 #endif
 
 #include "descs.h"
+#include "mmc.h"
 
 #undef CHIP_DEBUG_PRINT
 /* Turn-on extra printk debug for MAC core, dma and descriptors */