drm_hwcomposer: Initialize timeline_next to 1

drm_hwcomposer: Initialize timeline_next to 1

Initialize timeline_next to 1, because point 0 will be the very first
set operation. Since we increment every time set() is called,
initializing to 0 would cause an off-by-one error where
surfaceflinger would always composite on the front buffer.

Change-Id: I1e67c36864716595eb489286a7db3f1dcb04f67e
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-on: https://chrome-internal-review.googlesource.com/200735
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Allen Martin <amartin@nvidia.com>
Reviewed-by: Sean Paul <seanpaul@google.com>