ARM: EXYNOS4: Fix return type of local_timer_setup()

According to commmit af90f10d

 ("ARM: 6759/1: smp: Select
local timers vs broadcast timer support"), the return type
of local_timer_setup() should be int instead of void.

Reported-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>