Fixed unsigned to signed conversion warning

Change-Id: I6ff147e4418e8d0252bedfd1cf4a3bc3bc38ada7
diff --git a/include/armnn/TypesUtils.hpp b/include/armnn/TypesUtils.hpp
index c7dd856..68ad455 100644
--- a/include/armnn/TypesUtils.hpp
+++ b/include/armnn/TypesUtils.hpp
@@ -87,11 +87,11 @@
     }
 }
 
-template <int N>
+template <unsigned N>
 constexpr bool StrEqual(const char* strA, const char (&strB)[N])
 {
     bool isEqual = true;
-    for (int i = 0; isEqual && (i < N); ++i)
+    for (unsigned i = 0; isEqual && (i < N); ++i)
     {
         isEqual = (strA[i] == strB[i]);
     }