ThermalManagerService: only update thermal status for SKIN type thermistor

Skin thermistors are the ones to monitor long term thermal stress. The
public thermal API for app is meant to be used mitigation Tskin. This CL
will eliminate status update from other types of thermistors.

Test: atest ThermalManagerServiceTest
Change-Id: I333f358ee49fc83ad6d7b4944541f6fc428023ce