Fix OMAP touchscreen timer restart BUG.

kernel BUG at include/linux/timer.h:83!
[<c002ac60>] (__bug+0x0/0x58) from [<c01a3fbc>] (omap_ts_handler+0x60/0x78)
[<c01a3f5c>] (omap_ts_handler+0x0/0x78) from [<c00269fc>] (__do_irq+0x4c/0x8c)

which is:

static inline void add_timer(struct timer_list *timer)
{
        BUG_ON(timer_pending(timer));
        __mod_timer(timer, timer->expires);
Signed-off-by: Todd Poynor <tpoynor@mvista.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>