wifi: Fixing Nits

Changes in the CL to fix bugs found while integrating
with framework:
1. Added IWifiApIface.setCountryCode()
Bug: 34682168
2. Fixed documentation nits in .hal files.
Bug: 34468218
3. Changed roaming state enum values.
Bug: 34715231
4. Added log for EBUSY in legacyErrorToString()
Bug: 34715469
5. Remove "-Wno-unused parameter" from Android.mk
Bug: 34611289
6. Remove the erroneous |onFailure| callback invocation in wifi.cpp.
7. Add null terminations to strings passed to legacy HAL API's
8. Remove unused |IWifiStaIface.stopDebugPacketFateMonitoring|.

Test: Compiles
Change-Id: If3a3e2f360a378c59dc56b8bbe3a0c6d400b3bd8
diff --git a/wifi/1.0/default/Android.mk b/wifi/1.0/default/Android.mk
index f0c78ea..144c067 100644
--- a/wifi/1.0/default/Android.mk
+++ b/wifi/1.0/default/Android.mk
@@ -16,7 +16,7 @@
 include $(CLEAR_VARS)
 LOCAL_MODULE := android.hardware.wifi@1.0-service
 LOCAL_MODULE_RELATIVE_PATH := hw
-LOCAL_CPPFLAGS := -Wall -Wno-unused-parameter -Werror -Wextra
+LOCAL_CPPFLAGS := -Wall -Werror -Wextra
 LOCAL_SRC_FILES := \
     hidl_struct_util.cpp \
     service.cpp \