drm/i915: Fix warn in intel_display_power_*_domain() functions

The intel_display_power_*_domain() functions should always warn if a
default domain is returned as a fallback, fix this up. Spotted by Ville.

Fixes: 979e1b32 ("drm/i915: Sanitize the port -> DDI/AUX power domain mapping for each platform")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221114122251.21327-2-imre.deak@intel.com