As per the patch ("mailbox: Deprecate NULL mbox messages; Introduce
mbox_ring_doorbell()"), we want to switch all users of NULL mailbox
messages to use mbox_ring_doorbell().

This client only ever sent NULL messages, so the transition is
straightforward.

This client didn't previously call mbox_client_txdone() and it appears
that the mailboxes it hooks up with (qcom-apcs-ipc-mailbox.c or
qcom-ipcc.c) have both `txdone_irq` and `txdone_poll` as
false. Presumably this means the client was relying the mailbox core's
quirky behavior when sending NULL messages.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

(no changes since v1)

 drivers/irqchip/irq-qcom-mpm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-qcom-mpm.c b/drivers/irqchip/irq-qcom-mpm.c
index 83f31ea657b7..5b79d95bf1fb 100644
--- a/drivers/irqchip/irq-qcom-mpm.c
+++ b/drivers/irqchip/irq-qcom-mpm.c
@@ -302,7 +302,7 @@ static int mpm_pd_power_off(struct generic_pm_domain *genpd)
 		qcom_mpm_write(priv, MPM_REG_STATUS, i, 0);
 
 	/* Notify RPM to write vMPM into HW */
-	ret = mbox_send_message(priv->mbox_chan, NULL);
+	ret = mbox_ring_doorbell(priv->mbox_chan);
 	if (ret < 0)
 		return ret;
 
-- 
2.53.0.rc2.204.g2597b5adb4-goog