Rename Samsung ARM toolchain from ARMC6 to ARM

Author: Harrison Mutai

targets/targets.json

@@ -7503,7 +7503,7 @@
         "core": "Cortex-M7",
         "supported_toolchains": [
             "GCC_ARM",
-            "ARMC6"
+            "ARM"
         ],
         "default_toolchain": "GCC_ARM",
         "extra_labels": [