MGS-3940 gpu: imx: dpu-blit: fix first frame handler

MGS-3940 gpu: imx: dpu-blit: fix first frame handler

chrome browser hang is reproduced with mouse connected,
the first frame handler trigger the problem in below scenario:
tile (dprc-enable) --> linear (dprc->disable) --> tile (handle first frame wrongly).

need_handle_start is set following dprc_enable, need reset it with dprc_disable.

fix event trigger as previous implementation does not flush command sequence,
that will cause the obvious flicker when run glmark2 in full-screen.
also reduce bitter delay to 30us to improve blitter performance.

Signed-off-by: Xianzhong <xianzhong.li@nxp.com>