stat_timer only ever assigns the same function and data, so consolidate
to using timer_setup(), adjust callback, drop everything else used
to pass things around, and remove needless typedefs.

reset_timer is unused; remove it.

Cc: Hannes Reinecke <hare@suse.com>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>