Avoid "HAVE_CMOV not defined" warning.

patch by Christophe Mutricy, xtophe nxtelevision com

Originally committed as revision 7443 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/common.h

@@ -120,7 +120,7 @@ static inline int av_log2_16bit(unsigned int v)
 /* median of 3 */
 static inline int mid_pred(int a, int b, int c)
 {
-#if HAVE_CMOV
+#ifdef HAVE_CMOV
     int i=b;
     asm volatile(
         "cmp    %2, %1 \n\t"