msm_fb: display: add wfd clk ctrl in pipe_commit

mdp_clk_ctrl on is not called when commit is from overlay commit path
which can cause mdp hang. mdp_clk_ctrl off should be after mdp
overlay2 is done, so schedule a work in overlay2 done isr.

Change-Id: I94fd08da27cfda114f5cc0056a5103f0a9b772f6
Signed-off-by: Huaibin Yang <huaibiny@codeaurora.org>