OpenGLDevice: Disable PBOs completely on NVIDIA

Using PBOs for texture uploads in RGB5A1 format is **incredibly** slow on
NVIDIA. It causes stalls for 16ms+ when creating or waiting for syncs. It
looks like the driver gets stuck contended on a lock with a worker thread,
where the worker thread is buzzing away rotating 16-bit words right by one
bit. Even weirder, it looks like it's in jitted code???? And it's not even
vectorized???? This is the sort of rubbish I'd expect from Adreno or Mali,
seeing it on NVIDIA is very wtf.

src/util/opengl_device.cpp

@@ -502,6 +502,14 @@ bool OpenGLDevice::CheckFeatures(CreateFlags create_flags)
   {
     // glReadPixels() is about 2x as fast as glGetTextureSubImage() on NVIDIA drivers.
     m_use_get_texture_sub_image = false;
+
+    // Using PBOs for texture uploads in RGB5A1 format is **incredibly** slow on NVIDIA.
+    // It causes stalls for 16ms+ when creating or waiting for syncs. It looks like the driver gets
+    // stuck contended on a lock with a worker thread, where the worker thread is buzzing away
+    // rotating 16-bit words right by one bit. Even weirder, it looks like it's in jitted code????
+    // And it's not even vectorized???? This is the sort of rubbish I'd expect from Adreno or Mali,
+    // seeing it on NVIDIA is very wtf.
+    m_disable_pbo = true;
   }
 
   return true;