scsi: lpfc: Fix gcc -Wstringop-overread warning, again

I fixed a stringop-overread warning earlier this year, now a second copy of
the original code was added and the warning came back:

drivers/scsi/lpfc/lpfc_attr.c: In function 'lpfc_cmf_info_show':
drivers/scsi/lpfc/lpfc_attr.c:289:25: error: 'strnlen' specified bound 4095 exceeds source size 24 [-Werror=stringop-overread]
  289 |                         strnlen(LPFC_INFO_MORE_STR, PAGE_SIZE - 1),
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix it the same way as the other copy.

Link: https://lore.kernel.org/r/20210920095628.1191676-1-arnd@kernel.org
Fixes: ada48ba7 ("scsi: lpfc: Fix gcc -Wstringop-overread warning")
Fixes: 74a7baa2 ("scsi: lpfc: Add cmf_info sysfs entry")
Reviewed-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_attr.c

@@ -285,11 +285,8 @@ lpfc_cmf_info_show(struct device *dev, struct device_attribute *attr,
 				"6312 Catching potential buffer "
 				"overflow > PAGE_SIZE = %lu bytes\n",
 				PAGE_SIZE);
-		strscpy(buf + PAGE_SIZE - 1 -
-			strnlen(LPFC_INFO_MORE_STR, PAGE_SIZE - 1),
-			LPFC_INFO_MORE_STR,
-			strnlen(LPFC_INFO_MORE_STR, PAGE_SIZE - 1)
-			+ 1);
+		strscpy(buf + PAGE_SIZE - 1 - sizeof(LPFC_INFO_MORE_STR),
+			LPFC_INFO_MORE_STR, sizeof(LPFC_INFO_MORE_STR) + 1);
 	}
 	return len;
 }