linux-phytec-fsl

MLK-13862-2 epdc/pxp: imx6ull/imx6sll: enhance the LUT cleanup flow to avoid stalling display

- change setting for wfe_b to support new flow
  (note there's no wfe_a on i.mx6ull/i.mx6sll, while on i.mx7d wfe_a is used
  for this purpose)
- the underlying design policy change as follows (similar to i.mx7d).
  in previous flow, when all LUTs are used, the LUT cleanup operation
  need to wait for all the LUT to finish, it will not happen util last LUT
  is done. while in new flow, the cleanup operation does not need to wait
  for all LUTs to finish, instead it can start when there's LUT's done.
  The saved time is multiple LUT operation time.

Signed-off-by: Robby Cai <robby.cai@nxp.com>