Merge pull request #13381 from OpenNuvoton/nuvoton_m252_iot_5.15

Nuvoton: Update M252 target name (5.15)

Author: 0xc0170

targets/targets.json

@@ -9153,7 +9153,7 @@
         "mbed_ram_start": "0x20000000",
         "mbed_ram_size": "0xC000"
     },
-    "NUMAKER_M252KG": {
+    "NUMAKER_IOT_M252": {
         "core": "Cortex-M23",
         "trustzone": false,
         "is_disk_virtual": true,