mailbox: imx: Skip the suspend flag for i.MX7ULP

mailbox: imx: Skip the suspend flag for i.MX7ULP

In current imx-mailbox driver, the MU IRQ is configured with
'IRQF_NO_SUSPEND' flag set. So during linux suspend/resume flow,
the MU IRQ is always enabled. With commit 892cb524ae8a ("mailbox: imx:
fix wakeup failure from freeze mode"), if the MU IRQ is triggered after
the priv->suspended flag has been set, the system suspend will be
aborted.

On i.MX7ULP platform, certain drivers that depend on rpmsg may need
to send rpmsg request and receive an acknowledgment from the remote
core during the late_suspend stage. Early suspend abort is not
expected, and the i.MX7ULP already has additional hardware and
software to make sure the system can be wakeup from freeze mode
correctly when MU IRQ is trigger.

Skip the 'suspend' flag handling logic on i.MX7ULP to avoid the
early abort when doing suspend.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>