Enabled trace, added KW24D default driver

Author: Juhani Puurula

tools/test_configs/NanostackMACTester.json

@@ -1,6 +1,9 @@
 {
-    "macros": ["MBED_TRACE_LINE_LENGTH=200", "OS_TASKCNT=4", "OS_IDLESTKSIZE=32"],
+    "macros": ["MBED_TRACE_LINE_LENGTH=200", "OS_TASKCNT=4", "OS_IDLESTKSIZE=32", "MBED_CONF_MBED_TRACE_ENABLE=1"],
     "target_overrides": {
+        "KW24D": {
+            "mcr20a.provide-default": true
+        },
         "*": {
             "nanostack.configuration": "lowpan_host",
             "platform.stdio-convert-newlines": true,