libobs-opengl: Disable NV12/P010 on Windows

These formats are used for texture encoding but the OpenGL texture
encoding pipeline is not supported on Windows. This can also cause
failure to initialize on Windows so it's better to disable the formats.

libobs-opengl/gl-subsystem.c

@@ -1522,13 +1522,21 @@ void gs_swapchain_destroy(gs_swapchain_t *swapchain)
 bool device_nv12_available(gs_device_t *device)
 {
 	UNUSED_PARAMETER(device);
+#ifdef _WIN32
+	return false;
+#else
 	return true; // always a split R8,R8G8 texture.
+#endif
 }
 
 bool device_p010_available(gs_device_t *device)
 {
 	UNUSED_PARAMETER(device);
+#ifdef _WIN32
+	return false;
+#else
 	return true; // always a split R16,R16G16 texture.
+#endif
 }
 
 uint32_t gs_voltexture_get_width(const gs_texture_t *voltex)