drm/amdgpu/gfx9: use reset default for PA_SC_FIFO_SIZE

commit 25f09f85

 upstream.

Recommended by the hw team.

Reviewed-and-Tested-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>