Thermal: Remove tc1/tc2 in generic thermal layer.

Remove tc1/tc2 in generic thermal layer.
.get_trend() callback starts to take effect from this patch.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Valentin, Eduardo <eduardo.valentin@ti.com>