[ARM] 4813/1: Add SMP helper functions for clockevents support

This patch adds the smp_call_function_single and smp_timer_broadcast
functions and modifies ipi_timer to call the platform-specific function
local_timer_interrupt.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>