mailbox: imx: fix wakeup failure from freeze mode

Since IRQF_NO_SUSPEND used for imx mailbox driver, that means this irq
can't be used for wakeup source so that can't wakeup from freeze mode.
Add pm_system_wakeup() to wakeup from freeze mode.

Fixes: b7b2796b("mailbox: imx: ONLY IPC MU needs IRQF_NO_SUSPEND flag")
Reviewed-by: NJacky Bai <ping.bai@nxp.com>
Reviewed-by: NPeng Fan <peng.fan@nxp.com>
Signed-off-by: NRobin Gong <yibin.gong@nxp.com>
Signed-off-by: NPeng Fan <peng.fan@nxp.com>
Signed-off-by: NJassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/imx-mailbox.c

@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/suspend.h>
 #include <linux/slab.h>
 
 #define IMX_MU_CHANS		16
@@ -76,6 +77,7 @@ struct imx_mu_priv {
 	const struct imx_mu_dcfg	*dcfg;
 	struct clk		*clk;
 	int			irq;
+	bool			suspend;
 
 	u32 xcr[4];
 
@@ -334,6 +336,9 @@ static irqreturn_t imx_mu_isr(int irq, void *p)
 		return IRQ_NONE;
 	}
 
+	if (priv->suspend)
+		pm_system_wakeup();
+
 	return IRQ_HANDLED;
 }
 
@@ -702,6 +707,8 @@ static int __maybe_unused imx_mu_suspend_noirq(struct device *dev)
 			priv->xcr[i] = imx_mu_read(priv, priv->dcfg->xCR[i]);
 	}
 
+	priv->suspend = true;
+
 	return 0;
 }
 
@@ -723,6 +730,8 @@ static int __maybe_unused imx_mu_resume_noirq(struct device *dev)
 			imx_mu_write(priv, priv->xcr[i], priv->dcfg->xCR[i]);
 	}
 
+	priv->suspend = false;
+
 	return 0;
 }