ARM64: cpuidle: Replace cpu_suspend by the common ARM/ARM64 function

Call the common ARM/ARM64 'arm_cpuidle_suspend' instead of cpu_suspend function
which is specific to ARM64.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Kevin Hilman <khilman@linaro.org>
Acked-by: Rob Herring <robherring2@gmail.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>