Fixing problem with autodispatch when compiled with NVPTX target

ispc.h

@@ -176,14 +176,20 @@ public:
         also that __best_available_isa() needs to be updated if ISAs are
         added or the enumerant values are reordered.  */
     enum ISA {
+        SSE2    = 0,
+        SSE4    = 1,
+        AVX     = 2,
+        AVX11   = 3,
+        AVX2    = 4,
+        GENERIC = 5,
 #ifdef ISPC_NVPTX_ENABLED
-               NVPTX,
-#endif 
-#ifdef ISPC_ARM_ENABLED
-               NEON32, NEON16, NEON8,
+        NVPTX,
 #endif
-               SSE2, SSE4, AVX, AVX11, AVX2, GENERIC,
-               NUM_ISAS };
+#ifdef ISPC_ARM_ENABLED
+        NEON32, NEON16, NEON8,
+#endif
+        NUM_ISAS
+    };
 
     /** Initializes the given Target pointer for a target of the given
         name, if the name is a known target.  Returns true if the