Update all files possible under sched/timer to Apache 2.0. These excludes two files that have a Xiaomi copyright. Also, run all modified files through nxstyle to assure that the conform to the coding standard.
* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro
