drm/i915: Use CRTC index consistently during getting/putting CRTC power domains

The for_each_oldnew_intel_crtc_in_state() iterator index does match
crtc->pipe, but using the same thing as array index when getting and
putting CRTC power domains makes things clearer.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
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/20201130212200.2811939-2-imre.deak@intel.com

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

@@ -16377,8 +16377,8 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		intel_post_plane_update(state, crtc);
 
-		if (put_domains[i])
-			modeset_put_power_domains(dev_priv, put_domains[i]);
+		if (put_domains[crtc->pipe])
+			modeset_put_power_domains(dev_priv, put_domains[crtc->pipe]);
 
 		intel_modeset_verify_crtc(crtc, state, old_crtc_state, new_crtc_state);