ARM: cpuidle: Enable the ARM64 driver for both ARM32/ARM64
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: 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>