ESP8266: Add target override for M2351

Author: ccli8

components/wifi/esp8266-driver/mbed_lib.json

@@ -67,6 +67,14 @@
         "NUCLEO_F411RE": {
             "tx": "D8",
             "rx": "D2"
+        },
+        "NUMAKER_PFM_M2351_CM": {
+            "tx"                    : "PD_1",
+            "rx"                    : "PD_0",
+            "rst"                   : "PD_7",
+            "rts"                   : "PD_3",
+            "cts"                   : "PD_2",
+            "rst-pin-polarity"      : "1"
         }
     }
 }