power_supply: Register cooling device outside of probe

Registering the cooling device from the probe, can result in the
execution of get_property() function, before the probe is complete.

To avoid this, register the cooling device from a workqueue, instead of
registering in the probe.

Change-Id: Ic9279fd5ca5476df66baa6e0f302a7f3bd6b899b
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>