In order to avoid recursive ->detect->interrupt->detect->interrupt->...
we need to disable TV hotplug interrupts in
intel_tv.c:intel_tv_detect_type. We also need to enable the TV interrupt
detection and hotplug sequence properly in i915_irq.c.
Even if the TV encoder hasn't been fused off, we may not have a TV connector on
the platform. The BDB in the BIOS should give us this info in some cases.
Put off registering new outputs with sysfs until they're properly configured,
or we may get duplicates if the type hasn't been set yet (as is the case with
SDVO initialization). This also means moving de-registration into the cleanup
function instead of output destroy, since the latter occurs during the normal
course of setup when an output isn't found (and therefore not registered with
sysfs yet.