freedreno: glamor issue with x11 desktops

Seen with apps like gnome-terminal.. text doesn't update until you move a window.

Looks like we are getting a PIPE_FLUSH_DEFERRED flush, but then nothing actually triggers us to really flush? Nerf'ing the deferred flush mechanism "fixes" the problem.. but I think we'd prefer not to do that.

note that this does not seem to happen with Xwayland