freezer,sched: Clean saved_state when restoring it during thaw

Clean saved_state after using it during thaw. Cleaning the saved_state
allows us to avoid some unnecessary branches in ttwu_state_match.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20231120-freezer-state-multiple-thaws-v1-2-f2e1dd7ce5a2@quicinc.com