lavd/v4l2: reduce variable scope

device and cap are local to the loop iteration, there is no need for
them to retain their values. Especially for device it may be dangerous,
since it points to av_malloc'ed data.

libavdevice/v4l2.c

@@ -1019,8 +1019,6 @@ static int v4l2_get_device_list(AVFormatContext *ctx, AVDeviceInfoList *device_l
     struct video_data *s = ctx->priv_data;
     DIR *dir;
     struct dirent *entry;
-    AVDeviceInfo *device = NULL;
-    struct v4l2_capability cap;
     int ret = 0;
 
     if (!device_list)
@@ -1033,6 +1031,8 @@ static int v4l2_get_device_list(AVFormatContext *ctx, AVDeviceInfoList *device_l
         return ret;
     }
     while ((entry = readdir(dir))) {
+        AVDeviceInfo *device = NULL;
+        struct v4l2_capability cap;
         int fd = -1;
         char device_name[256];