exfat: release 5.8.4 version
- Zero out unused characters of FileName field to avoid a complaint from some fsck tool.
- Fix memory leak on error paths.
- Fix unnecessary VOL_DIRTY set when calling rmdir on non-empty directory.
- Call sync_filesystem() for read-only remount(Fix generic/452 test in xfstests)
- Add own fsync() to flush dirty metadata.
- fix overflow issue while calculating sector number.