drm/i915/gt: Drop false assertion on user_forcewake

The counter is removed from the pm wakeref count, but it remains intact
so that we can restore it upon resume. Ergo inside suspend, it may have
a value.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191104090158.2959-1-chris@chris-wilson.co.uk