scsi: scsi_debug: Fix uninitialized variable use

It appears that a typo has made it into the newly added code

drivers/scsi/scsi_debug.c:3035:3: error: variable 'len' is uninitialized when used here [-Werror,-Wuninitialized]
 3035 |                 len += resp_compression_m_pg(ap, pcontrol, target, devip->tape_dce);
      |                 ^~~

Replace the '+=' with the intended '=' here.

Fixes: 568354b ("scsi: scsi_debug: Add compression mode page for tapes")
Acked-by: Kai Mäkisara <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin K. Petersen <[email protected]>

Author: arndb

drivers/scsi/scsi_debug.c

@@ -3032,7 +3032,7 @@ static int resp_mode_sense(struct scsi_cmnd *scp,
 	case 0xf:	/* Compression Mode Page (tape) */
 		if (!is_tape)
 			goto bad_pcode;
-		len += resp_compression_m_pg(ap, pcontrol, target, devip->tape_dce);
+		len = resp_compression_m_pg(ap, pcontrol, target, devip->tape_dce);
 		offset += len;
 		break;
 	case 0x11:	/* Partition Mode Page (tape) */