mtp: use unsigned count/index

modules/services_discovery/mtp.c

@@ -71,7 +71,7 @@ typedef struct
 {
     uint64_t i_tracks_num;
     input_item_t **pp_items;
-    int i_count;
+    unsigned i_count;
     char *psz_name;
     uint32_t i_bus;
     uint8_t i_dev;
@@ -276,7 +276,7 @@ static void CloseDevice( services_discovery_t *p_sd )
 
     if( pp_items != NULL )
     {
-        for( int i_i = 0; i_i < p_sys->i_count; i_i++ )
+        for( unsigned i_i = 0; i_i < p_sys->i_count; i_i++ )
         {
             if( pp_items[i_i] != NULL )
             {