drivers: thermal: processor_thermal_device: Export sysfs interface for TCC offset

This change exports an interface to read tcc offset and allow writing if
the platform is not locked.

Refer to Intel SDM for details on the MSR: MSR_TEMPERATURE_TARGET.
Here TCC Activation Offset (R/W) bits allow temperature offset in degrees
in relation to TjMAX.

This change will be useful for improving performance from user space for
some platforms, if the current offset is not optimal.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Tested-by: Benjamin Berg <bberg@redhat.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>