x86: Use this_cpu_has for thermal_interrupt current cpu

It is more effective to use a segment prefix instead of calculating the
address of the current cpu area amd then testing flags.

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>