drm/msm: dpu: Simplify frame_done watchdog timeout calculation

drm/msm: dpu: Simplify frame_done watchdog timeout calculation

Instead of setting the timeout and then immediately reading it back
(along with the hand-rolled msecs_to_jiffies calculation), just
calculate it once and set it in both places at the same time.

Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128204306.95076-2-sean@poorly.run
Signed-off-by: Rob Clark <robdclark@chromium.org>