drm/i915: fix display power sw state reporting

drm/i915: fix display power sw state reporting

Atm, we refcount both power domains and power wells and
intel_display_power_enabled_sw() returns the power domain refcount. What
the callers are really interested in though is the sw state of the
underlying power wells. Due to this we will report incorrectly that a
given power domain is off if its power wells were enabled via another
power domain, for example POWER_DOMAIN_INIT which enables all power
wells.

As a fix return instead the state based on the refcount of all power
wells included in the passed in power domain.

References: https://bugs.freedesktop.org/show_bug.cgi?id=79505
References: https://bugs.freedesktop.org/show_bug.cgi?id=79038
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>