firmware: imx: scu-irq: fix RCU complaint after M4 partition reset

Use blocking_notifier_chain instead of atomic_notifier_chain, otherwise
there will be RCU complaint, because unregister/register_virtio_device()
will issue mbox message.

mbox_send_message() is blocking again after received M4 partition reset.

Actually, no need atomic notifier for scu irq notification since this
notifier is called in worker instead of interrupt handler.

[ 389.706645] i2c-rpmsg virtio0.rpmsg-i2c-channel.-1.2: i2c rpmsg driver is removed
[ 389.767362] Wait for remote ready timeout, use first_notify.
[ 389.774084] ------------[ cut here ]------------
[ 389.778729] WARNING: CPU: 0 PID: 397 at kernel/rcu/tree_plugin.h:293 rcu_note_context_switch+0x34/0x338
[ 389.788131] Modules linked in:
[ 389.791195] CPU: 0 PID: 397 Comm: kworker/0:13 Not tainted 5.4.0-rc5-02977-g08f78722f07b #26
[ 389.799633] Hardware name: Freescale i.MX8DXL MEK (DT)
[ 389.805481] Workqueue: events imx_scu_irq_work_handler

Signed-off-by: Robin Gong <[e-mail]>
Reviewed-by: Dong Aisheng <[e-mail]>
Signed-off-by: Peng Fan <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

drivers/firmware/imx/imx-scu-irq.c

···
 
 static struct imx_sc_ipc *imx_sc_irq_ipc_handle;
 static struct work_struct imx_sc_irq_work;
-static ATOMIC_NOTIFIER_HEAD(imx_scu_irq_notifier_chain);
+static BLOCKING_NOTIFIER_HEAD(imx_scu_irq_notifier_chain);
 
 int imx_scu_irq_register_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_register(
+	return blocking_notifier_chain_register(
 		&imx_scu_irq_notifier_chain, nb);
 }
 EXPORT_SYMBOL(imx_scu_irq_register_notifier);
 
 int imx_scu_irq_unregister_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_unregister(
+	return blocking_notifier_chain_unregister(
 		&imx_scu_irq_notifier_chain, nb);
 }
 EXPORT_SYMBOL(imx_scu_irq_unregister_notifier);
 
 static int imx_scu_irq_notifier_call_chain(unsigned long status, u8 *group)
 {
-	return atomic_notifier_call_chain(&imx_scu_irq_notifier_chain,
+	return blocking_notifier_call_chain(&imx_scu_irq_notifier_chain,
 		status, (void *)group);
 }