gl_stream_buffer/vk_staging_buffer_pool: Fix size check

Fix a tragic off-by-one condition that causes Vulkan's stream buffer to
think it's always full, using fallback memory. The OpenGL was also
affected by this bug to a lesser extent.

src/video_core/renderer_vulkan/vk_staging_buffer_pool.cpp

@@ -153,7 +153,7 @@ StagingBufferRef StagingBufferPool::GetStreamBuffer(size_t size) {
     used_iterator = iterator;
     free_iterator = std::max(free_iterator, iterator + size);
 
-    if (iterator + size > STREAM_BUFFER_SIZE) {
+    if (iterator + size >= STREAM_BUFFER_SIZE) {
         std::fill(sync_ticks.begin() + Region(used_iterator), sync_ticks.begin() + NUM_SYNCS,
                   current_tick);
         used_iterator = 0;