drm/mediatek: Add pm_runtime support for GCE power control

Call pm_runtime_resume_and_get() before accessing GCE hardware in
mbox_send_message(), and invoke pm_runtime_put_autosuspend() in the
cmdq callback to release the PM reference and start autosuspend for
GCE. This ensures correct power management for the GCE device.

Fixes: 8afe816b0c99 ("mailbox: mtk-cmdq-mailbox: Implement Runtime PM with autosuspend")
Signed-off-by: Jason-JH Lin <[e-mail]>
Reviewed-by: CK Hu <[e-mail]>
Link: https://patchwork.kernel.org/project/dri-devel/patch/[e-mail]/
Signed-off-by: Chun-Kuang Hu <[e-mail]>

drivers/gpu/drm/mediatek/mtk_crtc.c

···
 	unsigned int i;
 	unsigned long flags;
 
+	/* release GCE HW usage and start autosuspend */
+	pm_runtime_mark_last_busy(cmdq_cl->chan->mbox->dev);
+	pm_runtime_put_autosuspend(cmdq_cl->chan->mbox->dev);
+
 	if (data->sta < 0)
 		return;
 
···
 		spin_lock_irqsave(&mtk_crtc->config_lock, flags);
 		mtk_crtc->config_updating = false;
 		spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
+
+		if (pm_runtime_resume_and_get(mtk_crtc->cmdq_client.chan->mbox->dev) < 0)
+			goto update_config_out;
 
 		mbox_send_message(mtk_crtc->cmdq_client.chan, cmdq_handle);
 		mbox_client_txdone(mtk_crtc->cmdq_client.chan, 0);