drm/nouveau/kms/nv50-: init hpd_irq_lock for PIOR DP

Fixes OOPS on boards with ANX9805 DP encoders.

Cc: stable@vger.kernel.org # 6.4+
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230719044051.6975-3-skeggsb@gmail.com

Author: Ben Skeggs

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -1877,6 +1877,8 @@ nv50_pior_destroy(struct drm_encoder *encoder)
 	nvif_outp_dtor(&nv_encoder->outp);
 
 	drm_encoder_cleanup(encoder);
+
+	mutex_destroy(&nv_encoder->dp.hpd_irq_lock);
 	kfree(encoder);
 }
 
@@ -1921,6 +1923,8 @@ nv50_pior_create(struct drm_connector *connector, struct dcb_output *dcbe)
 	nv_encoder->i2c = ddc;
 	nv_encoder->aux = aux;
 
+	mutex_init(&nv_encoder->dp.hpd_irq_lock);
+
 	encoder = to_drm_encoder(nv_encoder);
 	encoder->possible_crtcs = dcbe->heads;
 	encoder->possible_clones = 0;