remove hacks to disable math or LDG functions.

hipamd/src/hip_ldg.cpp

@@ -20,7 +20,7 @@ THE SOFTWARE.
 #include <hc.hpp>
 #include"hcc_detail/hip_ldg.h"
 
-#if __hcc_workweek__ >= 16164 and defined (USE_LDG) 
+#if __hcc_workweek__ >= 16164 
 __device__ char                 __ldg(const char* ptr)
 {
     return ptr[0];