configure: fix cosmetic typo in check_mathfunc

Originally committed as revision 21748 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -669,7 +669,7 @@ EOF
 }
 
 check_mathfunc(){
-    log check_func "$@"
+    log check_mathfunc "$@"
     func=$1
     shift
     disable $func