Fixing compilation warnings

Change-Id: I3a1a361e6e8d40d2ac505b3c8d065c00224f1c2f
diff --git a/lib/ethosu_profiler/include/ethosu_profiler.hpp b/lib/ethosu_profiler/include/ethosu_profiler.hpp
index 503ebba..12c337c 100644
--- a/lib/ethosu_profiler/include/ethosu_profiler.hpp
+++ b/lib/ethosu_profiler/include/ethosu_profiler.hpp
@@ -39,8 +39,7 @@
     std::unique_ptr<const char *[]> tags_;
     std::unique_ptr<uint64_t[]> start_ticks_;
     std::unique_ptr<uint64_t[]> end_ticks_;
-
-    int num_events_ = 0;
+    size_t num_events_;
 
     TF_LITE_REMOVE_VIRTUAL_DELETE;
 };
diff --git a/lib/ethosu_profiler/src/ethosu_profiler.cpp b/lib/ethosu_profiler/src/ethosu_profiler.cpp
index bf4aae7..50b65f0 100644
--- a/lib/ethosu_profiler/src/ethosu_profiler.cpp
+++ b/lib/ethosu_profiler/src/ethosu_profiler.cpp
@@ -38,7 +38,7 @@
 
 namespace tflite {
 
-EthosUProfiler::EthosUProfiler(size_t max_events) : max_events_(max_events) {
+EthosUProfiler::EthosUProfiler(size_t max_events) : max_events_(max_events), num_events_(0) {
     tags_        = std::make_unique<const char *[]>(max_events_);
     start_ticks_ = std::make_unique<uint64_t[]>(max_events_);
     end_ticks_   = std::make_unique<uint64_t[]>(max_events_);
@@ -92,7 +92,8 @@
 
 uint64_t EthosUProfiler::GetTotalTicks() const {
     uint64_t ticks = 0;
-    for (int i = 0; i < num_events_; ++i) {
+
+    for (size_t i = 0; i < num_events_; ++i) {
         ticks += end_ticks_[i] - start_ticks_[i];
     }