texture_cache: tweak iteration tracking change

src/video_core/texture_cache/texture_cache.h

@@ -81,6 +81,7 @@ void TextureCache<P>::RunGarbageCollector() {
         if (num_iterations == 0) {
             return true;
         }
+        --num_iterations;
         auto& image = slot_images[image_id];
         if (True(image.flags & ImageFlagBits::IsDecoding)) {
             // This image is still being decoded, deleting it will invalidate the slot
@@ -95,7 +96,6 @@ void TextureCache<P>::RunGarbageCollector() {
         if (!high_priority_mode && must_download) {
             return false;
         }
-        --num_iterations;
         if (must_download) {
             auto map = runtime.DownloadStagingBuffer(image.unswizzled_size_bytes);
             const auto copies = FullDownloadCopies(image.info);