st: Remove obsolete scsi_tape.max_pfn

Its last user was removed 10 years ago, in commit
8b05b773 ("[SCSI] convert st to use scsi_execute_async").
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/st.h

@@ -148,8 +148,6 @@ struct scsi_tape {
 	int tape_type;
 	int long_timeout;	/* timeout for commands known to take long time */
 
-	unsigned long max_pfn;	/* the maximum page number reachable by the HBA */
-
 	/* Mode characteristics */
 	struct st_modedef modes[ST_NBR_MODES];
 	int current_mode;