Offload HAL Service: Enable errors for warnings

Update compile flags for this module so that warnings will report errors
during compilation. Also fixed one unused variable.

Bug: 32842314
Test: VTS
Change-Id: Ic48071c86bc81c93c44a4b0645134dc028f96b9e
diff --git a/wifi_offload/Android.bp b/wifi_offload/Android.bp
index 8ff578f..289ae26 100644
--- a/wifi_offload/Android.bp
+++ b/wifi_offload/Android.bp
@@ -24,7 +24,7 @@
         "offload_status_util.cpp",
         "offload_utils.cpp",
     ],
-    cflags: ["-Wall", "-Wextra"],
+    cflags: ["-Wall", "-Wextra", "-Werror"],
     shared_libs: [
         "libbase",
         "libhidlbase",
diff --git a/wifi_offload/Offload.h b/wifi_offload/Offload.h
index 4510f68..d5e9e6d 100644
--- a/wifi_offload/Offload.h
+++ b/wifi_offload/Offload.h
@@ -24,7 +24,7 @@
 
     // Death notification for callbacks.
     void serviceDied(uint64_t cookie,
-                     const android::wp<android::hidl::base::V1_0::IBase> &who) override {
+                     const android::wp<android::hidl::base::V1_0::IBase>& /* who */) override {
         cb_.clear();
         cb_function_(cookie);
     }