bwdif_vulkan: fix artifacts on vulkan decode images

Due to making the decode frames context use the coded size, the
filter started to display those artifacts as it reused the input frame's size.

Change it to instead output the real image size for images, not the input.

(cherry picked from commit 0e8abf2698)

libavfilter/vf_bwdif_vulkan.c

@@ -325,8 +325,8 @@ static int bwdif_vulkan_config_input(AVFilterLink *inlink)
 
     /* Defaults */
     vkctx->output_format = input_frames->sw_format;
-    vkctx->output_width  = input_frames->width;
-    vkctx->output_height = input_frames->height;
+    vkctx->output_width  = inlink->w;
+    vkctx->output_height = inlink->h;
 
     return 0;
 }