drm/i915: fixup tv load-detect on enabled but not active crtc

When fixing up the crt load detect code I've failed to notice the same
problem in the tv load detect code. Again, unconditionally use the
load detect pipe infrastructure, it gets things right.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>