fs/udf: Use DIV_ROUND_UP

The kernel.h macro DIV_ROUND_UP performs the computation (((n) + (d) - 1) /
(d)) but is perhaps more readable.

An extract of the semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@haskernel@
@@

#include <linux/kernel.h>

@depends on haskernel@
expression n,d;
@@

(
- (n + d - 1) / d
+ DIV_ROUND_UP(n,d)
|
- (n + (d - 1)) / d
+ DIV_ROUND_UP(n,d)
)

@depends on haskernel@
expression n,d;
@@

- DIV_ROUND_UP((n),d)
+ DIV_ROUND_UP(n,d)

@depends on haskernel@
expression n,d;
@@

- DIV_ROUND_UP(n,(d))
+ DIV_ROUND_UP(n,d)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/super.c

@@ -986,10 +986,9 @@ static void udf_load_fileset(struct super_block *sb, struct buffer_head *bh,
 int udf_compute_nr_groups(struct super_block *sb, u32 partition)
 {
 	struct udf_part_map *map = &UDF_SB(sb)->s_partmaps[partition];
-	return (map->s_partition_len +
-		(sizeof(struct spaceBitmapDesc) << 3) +
-		(sb->s_blocksize * 8) - 1) /
-		(sb->s_blocksize * 8);
+	return DIV_ROUND_UP(map->s_partition_len +
+			    (sizeof(struct spaceBitmapDesc) << 3),
+			    sb->s_blocksize * 8);
 }
 
 static struct udf_bitmap *udf_sb_alloc_bitmap(struct super_block *sb, u32 index)