g3dvl: remove unused vs output from create_ref_vert_shader

The position of the quad vertex is calculated in calc_position,
so we don't need the output here any more.

src/gallium/auxiliary/vl/vl_mc.c

@@ -105,7 +105,7 @@ create_ref_vert_shader(struct vl_mc *r)
    struct ureg_src mv_scale;
    struct ureg_src vmv[2];
    struct ureg_dst t_vpos;
-   struct ureg_dst o_vpos, o_vmv[2];
+   struct ureg_dst o_vmv[2];
    unsigned i;
 
    shader = ureg_create(TGSI_PROCESSOR_VERTEX);
@@ -120,9 +120,6 @@ create_ref_vert_shader(struct vl_mc *r)
       (float)MACROBLOCK_HEIGHT / r->buffer_height)
    );
 
-   /* XXX The position is not written, which may lead to undefined rendering.
-    * XXX This is a serious bug. */
-   o_vpos = ureg_DECL_output(shader, TGSI_SEMANTIC_POSITION, VS_O_VPOS);
    o_vmv[0] = ureg_DECL_output(shader, TGSI_SEMANTIC_GENERIC, VS_O_VTOP);
    o_vmv[1] = ureg_DECL_output(shader, TGSI_SEMANTIC_GENERIC, VS_O_VBOTTOM);