kms/impl-device: Use deadline timer for all updates

Not with VRR though, because the deadline timer fires at most every 33ms then.

Previously, the deadline timer was used only for cursor-only updates. Using it for other updates means they pick up the latest cursor position available at the deadline, resulting in the lowest possible input→output latency for cursor movement.

TTBOMK this unlocks the full potential of the KMS thread given the current atomic KMS API.