stmmac: enhance mmc counter management

For gmac3, the MMC addr map is: 0x100 - 0x2fc
For gmac4, the MMC addr map is: 0x700 - 0x8fc

So instead of adding 0x600 to the IO address when setup the mmc,
the RMON base address is saved inside the private structure and
then used to manage the counters.

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

drivers/net/ethernet/stmicro/stmmac/mmc.h

@@ -35,6 +35,10 @@
 						 * current value.*/
 #define MMC_CNTRL_PRESET		0x10
 #define MMC_CNTRL_FULL_HALF_PRESET	0x20
+
+#define MMC_GMAC4_OFFSET		0x700
+#define MMC_GMAC3_X_OFFSET		0x100
+
 struct stmmac_counters {
 	unsigned int mmc_tx_octetcount_gb;
 	unsigned int mmc_tx_framecount_gb;