Add EFM32GG11 Ethernet driver

Author: stevew817

features/lwipstack/mbed_lib.json

@@ -124,6 +124,9 @@
         },      
         "LPC546XX": {
             "mem-size": 36496
+        },
+        "EFM32GG11-STK3701": {
+            "mem-size": 36560
         }
     }
 }

features/netsocket/emac-drivers/TARGET_Silicon_Labs/mbed_lib.json

@@ -0,0 +1,34 @@
+{
+    "name": "sl-eth",
+    "config": {
+        "rmii-location": {
+            "help": "Location number to use for the RMII pins, see chip datasheet",
+            "value": null
+        },
+        "mdio-location": {
+            "help": "Location number to use for the MDIO pins, see chip datasheet",
+            "value": null
+        },
+        "refclk-location": {
+            "help": "Location number to use for the REFCLK output from CMU (CLKOUTSEL2), see chip datasheet",
+            "value": null
+        },
+        "phy-enable-pin": {
+            "help": "Pin attached to the PHY enable line",
+            "value": null
+        },
+        "phy-power-pin": {
+            "help": "Pin used to switch on power to the PHY. If not defined, we assume the PHY is always powered.",
+            "value": null
+        }
+    },
+    "target_overrides": {
+        "EFM32GG11_STK3701": {
+            "rmii-location": 1,
+            "mdio-location": 1,
+            "refclk-location": 5,
+            "phy-enable-pin": "PH7",
+            "phy-power-pin": "PI10"
+        }
+    }
+}