Add device bindings for cpuidle states for cpu devices.

Cc: <mkshah@codeaurora.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Raju P.L.S.S.S.N <rplsssn@codeaurora.org>
[amit: rename the idle-states to more generic names and fixups]
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <agross@kernel.org>