drm/i915/selftests: Nuke live_forcewake_domains selftest

drm/i915/selftests: Nuke live_forcewake_domains selftest

The live_forcewake_domains selftest doesn't really test anything
particularly sensible. It only runs on platforms that have RMbus
unclaimer error detection, but that only catches display registers
which the test doesn't even access.

I suppose if we really wanted to we might try to make the test
exercise the GT FIFO instead by writing GT registers as fast
as possible, and then checking GTFIFODBG to see if the FIFO has
overflowed. But dunno if there's much point in that. I think a
GT FIFO overflow might even be fatal to the machine.

So in its current for the test doesn't really make sense,
and it's in the way of moving all the RMbus noclaim stuff
to the display driver side. So let's just get rid of it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260323101609.8391-2-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>