Properly initialize IO statistics to avoid initial 0xFFFFFFF (-1) values.

Cleanup/simplify usage of pointer to statistics structure.
Signed-off-by: Joe Carnuccio <joe.carnuccio@qlogic.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>