ARM: 6887/1: Mark broadcast_timer_setup() __cpuinit

This function is only called by percpu_timer_setup() which is
also __cpuinit marked. Thus it's safe to mark this function as
__cpuinit as well.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>