jfs should use MAX_LFS_FILESIZE when calculating s_maxbytes

jfs had previously avoided the use of MAX_LFS_FILESIZE because it hadn't
accounted for the whole 32-bit index range on 32-bit systems.  That has
been fixed by commit 0cc3b0ec

 ("Clarify (and fix) MAX_LFS_FILESIZE
macros"), so we can simplify the code now.

Suggested by Andreas Dilger.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: jfs-discussion@lists.sourceforge.net
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>