drivers: thermal: cpu_cooling: Use Policy cpu as cdev ID

CPU cooling driver uses the IDA index to name the CPU cooling device.
This doesn't give the visibility of which cpufreq policy this particular
cooling device is managing.

Use the Policy CPU as the cooling device ID and this will have a one to
one correlation to the cpufreq policy ID.

Change-Id: I1ee0ac383328f4eb7e3f83e970d03af97aba9953
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>