Split repaint into two stages, as implied by the grouped-repaint
interface: drm_output_repaint generates the repaint state only, and
drm_repaint_flush applies it.

This also moves DPMS into output state. Previously, the usual way to
DPMS off was that repaint would be called and apply its state, followed
by set_dpms being called afterwards to push the DPMS state separately.
As this happens before the repaint_flush hook, with no change to DPMS we
would set DPMS off, then immediately re-enable the output by posting the
repaint. Not ideal.

Moving DPMS application at the same time complicates this patch, but I
couldn't find a way to split it; if we keep set_dpms before begin_flush
then we break DPMS off, or if we try to move DPMS to output state before
using the repaint flush, we get stuck as the repaint hook generates an
asynchronous state update, followed immediately by set_dpms generating a
synchronous state update.

In drm_output_update_complete, the *_pending flags are cleared
before any of the pending actions are taken; this ensures that the
actions cannot recurse.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>