md/bitmap: white space clean up and similar.

Fixes some whitespace problems
Fixed some checkpatch.pl complaints.
Replaced kmalloc ... memset(0), with kzalloc
Fixed an unlikely memory leak on an error path.
Reformatted a number of 'if/else' sets, sometimes
replacing goto with an else clause.
Removed some old comments and commented-out code.

Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.h

@@ -319,7 +319,7 @@ struct mddev_s
 							 */
 		struct mutex		mutex;
 		unsigned long		chunksize;
-		unsigned long		daemon_sleep; /* how many seconds between updates? */
+		unsigned long		daemon_sleep; /* how many jiffies between updates? */
 		unsigned long		max_write_behind; /* write-behind mode */
 		int			external;
 	} bitmap_info;