update hw_blend_state.independent_blend_enable after setting state

Otherwise, we'll end up destroying the state when restoring after
clears.

Fixes these test-cases:
dEQP-GLES31.functional.draw_buffers_indexed.random.max_required_draw_buffers.7
dEQP-GLES31.functional.draw_buffers_indexed.random.max_implementation_draw_buffers.13

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/vrend_renderer.c

@@ -3611,6 +3611,7 @@ static void vrend_hw_emit_blend(struct vrend_context *ctx, struct pipe_blend_sta
                      state->rt[0].colormask & PIPE_MASK_A ? GL_TRUE : GL_FALSE);
       }
    }
+   ctx->sub->hw_blend_state.independent_blend_enable = state->independent_blend_enable;
 
    if (vrend_state.have_multisample) {
       if (state->alpha_to_coverage)