MGS-3806: clocksource: tpm: make sure returning -ETIME case correct

MGS-3806: clocksource: tpm: make sure returning -ETIME case correct

Incorrect condition check causes -ETIME return only
happen when next event is equal to current counter, and
it would cause various system issue like RCU stalls etc.,
the correct case should be whenever next event is less
than current counter, -ETIME should be returned. Correct
the type cast during return condition check to make it
work right.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Bai Ping <ping.bai@nxp.com>