ftgmac100: Add pause frames configuration and support

Hopefully my understanding of how the hardware works is correct,
as the documentation isn't completely clear. So far I have seen
no obvious issue. Pause seem to also work with NC-SI.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/faraday/ftgmac100.h

@@ -198,6 +198,13 @@
 #define FTGMAC100_PHYDATA_MIIWDATA(x)		((x) & 0xffff)
 #define FTGMAC100_PHYDATA_MIIRDATA(phydata)	(((phydata) >> 16) & 0xffff)
 
+/*
+ * Flow control register
+ */
+#define FTGMAC100_FCR_FC_EN		(1 << 0)
+#define FTGMAC100_FCR_FCTHR_EN		(1 << 2)
+#define FTGMAC100_FCR_PAUSE_TIME(x)	(((x) & 0xffff) << 16)
+
 /*
  * Transmit descriptor, aligned to 16 bytes
  */