Adds missing interface for vendor.thermal-hal-2-0-mock.

init_rc files require the entire interface inheritance hierarchy to
be listed, since e.g. all 1.0::IThermal functions are also implemented
by 2.0::IThermal.

Bug: 118016875
Test: builds & passes existing tests.
Change-Id: I4b00d9e1aa02f45dd1affe77d680920c7f04a4c4