[cmake] Added target static_check for static code analysis

- Added static code analysis using cppcheck
- Fixed couple of warnings reported by cppcheck

Change-Id: Ie3b9b06e95ada322e7dc2ce3d6b91831e870198d

src/hip_fp16.cpp

@@ -448,7 +448,7 @@ __device__  __half2 __lowhigh2highlow(const __half2 a) {
 
 __device__  __half2 __lows2half2(const __half2 a, const __half2 b) {
   __half2 c;
-  c.y = a.x;
+  c.x = a.x;
   c.y = b.x;
   return c;
 }

src/macro_based_grid_launch.inl

@@ -89,9 +89,8 @@ namespace hip_impl
         stream->lockclose_postKernelCommand(kernel_name, acc_v);
 
         delete static_cast<L*>(locked_stream);
-        locked_stream = nullptr;
         if(HIP_PROFILE_API) {
             MARKER_END();
         }
     }
-}
+}