glsl/ast: assign explicit_xfb_buffer from correct place

This fixes:
GL44-CTS.tessellation_shader.tessellation_control_to_tessellation_evaluation.data_pass_through

As the OUT_TC interface structures weren't matching because
one of them had explicit_xfb_buffer set when it shouldn't.

Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
1 file changed