Sanitize ->fsync() for FAT

* mark directory data blocks as assoc. metadata
* add new inode to deal with FAT, mark FAT blocks as assoc. metadata of that
* now ->fsync() is trivial both for files and directories

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/fat/dir.c
Simple merge

diff --cc fs/fat/fat.h
Simple merge

diff --cc fs/fat/fatent.c
Simple merge

diff --cc fs/fat/file.c
Simple merge

diff --cc fs/fat/inode.c
Simple merge

diff --cc fs/fat/namei_msdos.c
Simple merge

diff --cc fs/fat/namei_vfat.c
Simple merge