scsi: mpt3sas: fix format overflow warning

We print the driver name into one string and then add and ID
and copy it into a second string of the same length, at which
point gcc complains about a possible overflow:

drivers/scsi/mpt3sas/mpt3sas_scsih.c: In function '_scsih_probe':
drivers/scsi/mpt3sas/mpt3sas_scsih.c:8884:21: error: '_cm' directive writing 3 bytes into a region of size between 1 and 32 [-Werror=format-overflow=]
printf(ioc->name, "%s_cm%d", ioc->driver_name, ioc->id);
                  ^~~~~~~~~
drivers/scsi/mpt3sas/mpt3sas_scsih.c:8884:21: note: directive argument in the range [0, 255]
drivers/scsi/mpt3sas/mpt3sas_scsih.c:8884:2: note: 'sprintf' output between 5 and 38 bytes into a destination of size 32
  sprintf(ioc->name, "%s_cm%d", ioc->driver_name, ioc->id);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Making the first string shorter is sufficient to avoid the
warning here, as we know it can only contain either "mpt2sas"
or "mpt3sas".
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpt3sas/mpt3sas_base.h

@@ -970,7 +970,7 @@ struct MPT3SAS_ADAPTER {
 	u8		id;
 	int		cpu_count;
 	char		name[MPT_NAME_LENGTH];
-	char		driver_name[MPT_NAME_LENGTH];
+	char		driver_name[MPT_NAME_LENGTH - 8];
 	char		tmp_string[MPT_STRING_LENGTH];
 	struct pci_dev	*pdev;
 	Mpi2SystemInterfaceRegs_t __iomem *chip;