Now the only user who are using generic_ffs() is ntfs filesystem.  This patch
isolates generic_ffs() as ntfs_ffs() for ntfs.
Signed-off-by: NAkinobu Mita <mita@miraclelinux.com>
Cc: Anton Altaparmakov <aia21@cantab.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>