avfilter/f_perms: Change enums to int, which are accessed via AVOption as int

This fixes depending on implementation defined behavior
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/f_perms.c

@@ -37,7 +37,7 @@ typedef struct {
     const AVClass *class;
     AVLFG lfg;
     int64_t random_seed;
-    enum mode mode;
+    int mode;
 } PermsContext;
 
 #define OFFSET(x) offsetof(PermsContext, x)