msm: thermal: Keep core_control_mask coincident with boot_cpu_mask

Update core_control_mask according to boot_cpu_mask to make sure
the hotplug activities in thermal driver can only happen among the
CPUs under boot_cpu_mask.

Change-Id: Ic8bd319b94b234e913d89b65736ff287706db7c1
Signed-off-by: Xiaocheng Li <lix@codeaurora.org>