intel: Remove a gratuitous MI_FLUSH after clearing with a blit.

The 3D destination shares the same cache so we don't have any trouble with
the later commands needing the writes flushed inside of the same batchbuffer.

src/mesa/drivers/dri/intel/intel_blit.c

@@ -562,7 +562,6 @@ intelClearWithBlit(GLcontext *ctx, GLbitfield mask)
             }
          }
       }
-      intel_batchbuffer_emit_mi_flush(intel->batch);
    }
 
    UNLOCK_HARDWARE(intel);