ARM: at91: remove wait_for_interrupt definition

ARM: at91: remove wait_for_interrupt definition

All the "wait_for_interrupt" definition are aliases to cpu_do_idle.
Only the rm9200 has an asm routine to switch to wfi. But the cpu_do_idle
for this platform has exactly the same asm routine.

arch/arm/mm/proc-arm920.S
..
ENTRY(cpu_arm920_do_idle)
        mcr     p15, 0, r0, c7, c0, 4           @ Wait for interrupt
..

Then it is safe to invoke cpu_do_idle for this platform. As all the
wait_for_interrupts are definition for cpu_do_idle, let's remove it
and replace its invokation by cpu_do_idle.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>