scsi: pm8001: Avoid -Wrestrict warning

scsi: pm8001: Avoid -Wrestrict warning

On some configurations, gcc warns about overlapping source and destination
arguments to snprintf:

drivers/scsi/pm8001/pm8001_init.c: In function 'pm8001_request_msix':
drivers/scsi/pm8001/pm8001_init.c:977:3: error: 'snprintf' argument 4 may overlap destination object 'pm8001_ha' [-Werror=restrict]
  977 |   snprintf(drvname, len, "%s-%d", pm8001_ha->name, i);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/scsi/pm8001/pm8001_init.c:962:56: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
  962 | static u32 pm8001_request_msix(struct pm8001_hba_info *pm8001_ha)
      |                                ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~

I first assumed this was a gcc bug, as that should not happen, but a
reduced test case makes it clear that this happens when the loop counter is
not bounded by the array size.

Help the compiler out by adding an explicit limit here to make the code
slightly more robust and avoid the warning.

Link: https://godbolt.org/z/6T1qPM
Link: https://lore.kernel.org/r/20210323125458.1825564-1-arnd@kernel.org
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>