drm/i915: move debug output back to the right place

When adding the pipe config computation step I've accidentally moved
this a bit away. Which momentarily confused me since the pipe config
step rejected some modesetting operations I expected and so left me
looking in vain for that debug output.

v2: Move the debug output into the right function to prevent this from
happening again.

v3: Make it compile (Ville). Also reorder the patch so that the two
bugfixes are first.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>