jfs_dmap.[ch]: trivial typo fix: s/heigth/height/g

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Jiri Kosina <trivial@kernel.org>
Cc: André Goddard Rosa <andre.goddard@gmail.com>
Cc: jfs-discussion@lists.sourceforge.net