mn10300: Switch do_timer() to xtimer_update()

Only one CPU gets the timer interrupt so mn10300_last_tsc does not
need to be protected by xtime lock. Remove xtime lovking and use
xtime_update() which does the locking itself.
Signed-off-by: Torben Hohn <torbenh@gmx.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
LKML-Reference: <20110127150011.23248.62040.stgit@localhost>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/mn10300/kernel/time.c

@@ -104,8 +104,6 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id)
 	unsigned tsc, elapse;
 	irqreturn_t ret;
 
-	write_seqlock(&xtime_lock);
-
 	while (tsc = get_cycles(),
 	       elapse = tsc - mn10300_last_tsc, /* time elapsed since last
 						 * tick */
@@ -114,11 +112,9 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id)
 		mn10300_last_tsc += MN10300_TSC_PER_HZ;
 
 		/* advance the kernel's time tracking system */
-		do_timer(1);
+		xtime_update(1);
 	}
 
-	write_sequnlock(&xtime_lock);
-
 	ret = local_timer_interrupt();
 #ifdef CONFIG_SMP
 	send_IPI_allbutself(LOCAL_TIMER_IPI);