drm/i915/dvo: call ->mode_set callback only when the port is running

drm/i915/dvo: call ->mode_set callback only when the port is running

commit 48f34e10169dbb3dd7a19af64e328492b7f54af4 upstream.

The ns2501 controller seems to need the dpll and dvo port to accept
the timing update commands. Quick testing on my x30 here seems to
indicate that other dvo controllers don't mind. So let's move the
->mode_set callback to a place where we have the port up and running
already.

Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Thomas Richter <thor@math.tu-berlin.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>