Remove unnecessary division and modulo from ext3 code in often used paths. 
Without the patch an oprofile of dbench load shows ext3_get_group_desc()
uses 0.84% and ext3_group_sparse() 1.51%, with the patch the numbers are
0.33% and 0.27% respectively.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>