scsi: core: remove reference to scsi_show_extd_sense()

In commit 21045519 ("scsi: use per-cpu buffer for formatting sense"),
function scsi_show_extd_sense() was removed, switching use over to
scsi_format_extd_sense().  Remove last reference to scsi_show_extd_sense()
in include/scsi/scsi_dbg.h.

Signed-off-by: John Pittman <jpittman@redhat.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>