drm/i915/sdvo: Always add a 30ms delay to make SDVO TV detection reliable

Commit d09c23de

 intended to add a 30ms delay to give the ADD time to
detect any TVs connected. However, it used the sdvo->is_tv flag to do so
which is dependent upon the previous detection result and not whether the
output supports TVs.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org