ARM32 and ARM64 have the same DT definitions and the same approaches.

The generic ARM cpuidle driver can be put in common for those two
architectures.
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: NKevin Hilman <khilman@linaro.org>
Acked-by: NRob Herring <robherring2@gmail.com>
Acked-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>