h8300: Switch do_timer() to xtime_update()

xtime_update() takes the xtime_lock itself.

Signed-off-by: Torben Hohn <torbenh@gmx.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: johnstul@us.ibm.com
Cc: hch@infradead.org
Cc: yong.zhang0@gmail.com
LKML-Reference: <20110127145951.23248.92727.stgit@localhost>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>