u_math.h: Remove redundant mingw32 ffs definition

Signed-off-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Brian Paul <brianp@vmware.com>

src/gallium/auxiliary/util/u_math.h

@@ -413,10 +413,6 @@ unsigned ffs( unsigned u )
 #define ffs __builtin_ffs
 #endif
 
-#ifdef __MINGW32__
-#define ffs __builtin_ffs
-#endif
-
 
 /* Could also binary search for the highest bit.
  */