usb: chipidea: fix deadlock in ci_otg_del_timer

There is a deadlock in ci_otg_del_timer(), the process is
shown below:

(thread 1) | (thread 2)
ci_otg_del_timer() | ci_otg_hrtimer_func()
... |
spin_lock_irqsave() //(1) | ...
... |
hrtimer_cancel() | spin_lock_irqsave() //(2)
(block forever)

We hold ci->lock in position (1) and use hrtimer_cancel() to
wait ci_otg_hrtimer_func() to stop, but ci_otg_hrtimer_func()
also need ci->lock in position (2). As a result, the
hrtimer_cancel() in ci_otg_del_timer() will be blocked forever.

This patch extracts hrtimer_cancel() from the protection of
spin_lock_irqsave() in order that the ci_otg_hrtimer_func()
could obtain the ci->lock.

What`s more, there will be no race happen. Because the
"next_timer" is always under the protection of
spin_lock_irqsave() and we only check whether "next_timer"
equals to NUM_OTG_FSM_TIMERS in the following code.

Fixes: 3a316ec4c91c ("usb: chipidea: use hrtimer for otg fsm timers")
Cc: stable <[e-mail]>
Signed-off-by: Duoming Zhou <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/chipidea/otg_fsm.c

···
 	ci->enabled_otg_timer_bits &= ~(1 << t);
 	if (ci->next_otg_timer == t) {
 		if (ci->enabled_otg_timer_bits == 0) {
+			spin_unlock_irqrestore(&ci->lock, flags);
 			/* No enabled timers after delete it */
 			hrtimer_cancel(&ci->otg_fsm_hrtimer);
+			spin_lock_irqsave(&ci->lock, flags);
 			ci->next_otg_timer = NUM_OTG_FSM_TIMERS;
 		} else {
 			/* Find the next timer */