[NUCLEO_F746ZG] Enable Ethernet feature for mbed-os

Author: adustm

hal/targets.json

@@ -833,7 +833,8 @@
             }
         },
         "detect_code": ["0816"],
-        "device_has": ["ANALOGIN", "ANALOGOUT", "CAN", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"]
+        "device_has": ["ANALOGIN", "ANALOGOUT", "CAN", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
+        "features": ["IPV4"]
     },
     "NUCLEO_L031K6": {
         "inherits": ["Target"],