glsl/ast: assign explicit_xfb_buffer from correct place
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 <5dd83789ef3714029244367ba1ca09f1d7627408@collabora.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler