In order for CPUidle to work on SMP systems, an implementation of
cpu_idle_wait() is needed.

This patch duplicates the x86 implementation of cpu_idle_wait() for
ARM.
Tested-by: NColin Cross <ccross@android.com>
Signed-off-by: NKevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>