In detecting the case where we actually do need to re-emit LRZ state
(due to new batch), we were checking `ctx->last.dirty` to detect when
we cannot trust previous state.  But this is cleared before we check
it.

Move where it is cleared to the end of the draw_vbo() path.

Fixes: dfa702e9

 ("freedreno/a6xx: limit LRZ state emit")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <mesa/mesa!4842>