drm/msm: check for equals 0 only

wait_for_completion_timeout() returns 0 on timeout and aleast 1 otherwise
so checking for < makes no sense here.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>