Use findLSB as well in bitfield test.

reference/shaders/comp/bitfield.comp

@@ -14,6 +14,6 @@ void main()
     int v0 = bitCount(u);
     int v1 = bitCount(s);
     int v2 = findMSB(u);
-    int v3 = findMSB(s);
+    int v3 = findLSB(s);
 }
 

shaders/comp/bitfield.comp

@@ -17,5 +17,5 @@ void main()
    int v1 = bitCount(s);
 
    int v2 = findMSB(u);
-   int v3 = findMSB(s);
+   int v3 = findLSB(s);
 }