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

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 <yibin.gong@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>