drm/i915: Don't check power domains state in intel_power_domains_init_hw()

During power domains initialization we acquire power well references for
power wells in the INIT power domain. The rest of power wells - which
BIOS could have left enabled - we can only acquire references as needed
during display HW readout and so must defer sanitization until then
(also implying that we must always do HW readout to cleanup unused power
wells).

Thus during initialization these latter power wells can have a refcount
of 0 while still being enabled. To avoid the false-positive state
mismatch error this causes remove the check from
intel_power_domains_init_hw() and rely on the state check in
intel_power_domains_enable() which follows the HW readout.

v2:
- Add comment to log and code clarifying how unused power wells get
  disabled. (Chris)

Fixes: 6dfc4a8f

 ("drm/i915: Verify power domains after enabling them")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
References: https://bugs.freedesktop.org/show_bug.cgi?id=107411
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180828122231.14336-1-imre.deak@intel.com