drivers: thermal: cpu_cooling: Use CPU ID as cooling device ID

CPU cooling device will use IDR to get integer numbers for defining
the CPU cooling device ID. With having one cooling device per policy,
it will be tough to correlate a cooling device ID to the policy it is
mitigating.

Use the CPU ID from the policy as cooling device ID, which will allow
easy mapping of cooling device to CPU.

Change-Id: I249112ac467b84aea4f08466d91d6be520fbbc14
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>