cpuidle: big.LITTLE: add of_device_id structure

This driver will be used by many big.Little Soc's. As of now it does
string matching of hardcoded compatible string to init the driver. This
comparison list will keep on growing with addition of new SoC's.
Hence add of_device_id structure to collect the compatible strings of
SoC's using this driver.

Signed-off-by: Chander Kashyap <chander.kashyap@linaro.org>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>