usb: musb: Fix external abort on non-linefetch for musb_irq_work()

While testing musb host mode cable plugging on a BeagleBone, I came across this
error:

Unhandled fault: external abort on non-linefetch (0x1008) at 0xd1dcfc60
...
[<bf668390>] (musb_default_readb [musb_hdrc]) from [<bf668578>] (musb_irq_work+0x1c/0x180 [musb_hdrc])
[<bf668578>] (musb_irq_work [musb_hdrc]) from [<c0156554>] (process_one_work+0x2b4/0x808)
[<c0156554>] (process_one_work) from [<c015767c>] (worker_thread+0x3c/0x550)
[<c015767c>] (worker_thread) from [<c015d568>] (kthread+0x104/0x148)
[<c015d568>] (kthread) from [<c01078d0>] (ret_from_fork+0x14/0x24)

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_core.c

@@ -1925,6 +1925,14 @@ static void musb_pm_runtime_check_session(struct musb *musb)
 static void musb_irq_work(struct work_struct *data)
 {
 	struct musb *musb = container_of(data, struct musb, irq_work.work);
+	int error;
+
+	error = pm_runtime_get_sync(musb->controller);
+	if (error < 0) {
+		dev_err(musb->controller, "Could not enable: %i\n", error);
+
+		return;
+	}
 
 	musb_pm_runtime_check_session(musb);
 
@@ -1932,6 +1940,9 @@ static void musb_irq_work(struct work_struct *data)
 		musb->xceiv_old_state = musb->xceiv->otg->state;
 		sysfs_notify(&musb->controller->kobj, NULL, "mode");
 	}
+
+	pm_runtime_mark_last_busy(musb->controller);
+	pm_runtime_put_autosuspend(musb->controller);
 }
 
 static void musb_recover_from_babble(struct musb *musb)