Cleanup code for flush/close command.
Check the STILL_RUNNING after send the command.
- Previous version, wave5_vpu_hw_flush_instance() never return -EBUSY value, because wave5_vpu_hw_flush_instance() is finished before checking the fail reason.
Removed redundant code.
- Driver is updated to retry close command in dec_close() instead of release_device().
- Do not need to retry dec/enc_close function in release_device().