lima: delay plbu head command generation to flush stage (v2)

lima: delay plbu head command generation to flush stage (v2)

Prepare for multi submit in which case only know the plb_index when
final flush. Another need for this is proper reload detection: only
when flush stage can we know if need to do reload, because user may
first clear depth, then color individually, so we don't know if need
to pack repload plbu cmd when first clear depth.

v2:
move lima_update_submit_wb before ctx->resolve change for lima_ctx_dirty
to work in lima_submit_wb.

Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3755>