ENGR00154346 UART: fix uart deadlock

ENGR00154346 UART: fix uart deadlock

UART hold the following locks in order of:

imx_set_termios():
--> spin_lock_irqsave(&sport->port.lock, flags)
    del_timer_sync(&sport->timer);
	--> spin_lock(timer->base->lock);
    	--> spin_unlock(timer->base->lock);
    spin_unlock_irqrestore(&sport->port.lock);

while when imx_timeout() may invoked in following stack:
run_timer_softirq():
--> spin_lock_irqsave(timer->base->lock, flags);
    imx_timeout();
	--> spin_lock_irqsave(&sport->port.lock, flags);
	    ...;
	--> spin_unlock_irqrestore(&sport->port.lock, flags);
    spin_unlock_irqrestore(timer->base->lock, flags);

the above two cases hold lock with revert order, may
deadlock in SMP platform.

Signed-off-by: Zeng Zhaoming <b32542@freescale.com>