Add __hip_pinned_shadow__ for hip-clang and fix texture reference tests (#1200)

include/hip/hcc_detail/host_defines.h

@@ -72,6 +72,7 @@ THE SOFTWARE.
 
 #define __noinline__ __attribute__((noinline))
 #define __forceinline__ inline __attribute__((always_inline))
+#define __hip_pinned_shadow__ __attribute__((hip_pinned_shadow))
 
 #else