ARM: 7700/2: Make cpu_init() notrace

On resume from CPU power down any trace hooks enabled in cpu_init()
will get called before that function has done set_my_cpu_offset(),
so any use of per-cpu variables by trace hook code will cause bad
things to happen. Prevent this by marking the function notrace.

This fixes lockups/crashes seen when enabling function tracer on TC2
with the not yet mainlined cpuidle driver.

Signed-off-by: Jon Medhurst <tixy@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>