scsi: qla1280: Remove redundant assignment to variable 'mr'

The variable 'mr' being assigned a value that is never read, the assignment
is redundant and can be removed.

Cleans up clang scan build warning:

drivers/scsi/qla1280.c:2481:2: warning: Value stored to 'mr' is never
read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20240215153533.2067413-1-colin.i.king@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: ColinIanKing

drivers/scsi/qla1280.c

@@ -2478,7 +2478,6 @@ qla1280_mailbox_command(struct scsi_qla_host *ha, uint8_t mr, uint16_t *mb)
 	/* Load return mailbox registers. */
 	optr = mb;
 	iptr = (uint16_t *) &ha->mailbox_out[0];
-	mr = MAILBOX_REGISTER_COUNT;
 	memcpy(optr, iptr, MAILBOX_REGISTER_COUNT * sizeof(uint16_t));
 
 	if (ha->flags.reset_marker)