mesa: remove spurious flush in _mesa_Viewport()

I don't think this is actually required, if the viewport
values are different from the ones stored in the context, we
already flush and trigger _NEW_VIEWPORT in
set_viewport_no_notify().

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/viewport.c

@@ -129,7 +129,6 @@ void GLAPIENTRY
 _mesa_Viewport(GLint x, GLint y, GLsizei width, GLsizei height)
 {
    GET_CURRENT_CONTEXT(ctx);
-   FLUSH_VERTICES(ctx, 0);
 
    if (MESA_VERBOSE & VERBOSE_API)
       _mesa_debug(ctx, "glViewport %d %d %d %d\n", x, y, width, height);