Only actually take the lock for the immediate context. According to the
d3d11 documentation, operations on device contexts are not thread safe,
and testing on Windows confirms this.
Signed-off-by: Jan Sikorski <jsikorski@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>