drm/i915: Do not set any power wells when there is no display

Power wells are only part of display block and not necessary when
running a headless driver.

Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210408203150.237947-2-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_display_power.c

@@ -4674,7 +4674,10 @@ int intel_power_domains_init(struct drm_i915_private *dev_priv)
 	 * The enabling order will be from lower to higher indexed wells,
 	 * the disabling order is reversed.
 	 */
-	if (IS_ALDERLAKE_S(dev_priv) || IS_DG1(dev_priv)) {
+	if (!HAS_DISPLAY(dev_priv)) {
+		power_domains->power_well_count = 0;
+		err = 0;
+	} else if (IS_ALDERLAKE_S(dev_priv) || IS_DG1(dev_priv)) {
 		err = set_power_wells_mask(power_domains, tgl_power_wells,
 					   BIT_ULL(TGL_DISP_PW_TC_COLD_OFF));
 	} else if (IS_ROCKETLAKE(dev_priv)) {