ibmvnic: replace deprecated strncpy with strscpy

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

NUL-padding is not required as the buffer is already memset to 0:
|       memset(adapter->fw_version, 0, 32);

Note that another usage of strscpy exists on the same buffer:
|       strscpy((char *)adapter->fw_version, "N/A", sizeof(adapter->fw_version));

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -5247,7 +5247,8 @@ static void handle_vpd_rsp(union ibmvnic_crq *crq,
 	/* copy firmware version string from vpd into adapter */
 	if ((substr + 3 + fw_level_len) <
 	    (adapter->vpd->buff + adapter->vpd->len)) {
-		strncpy((char *)adapter->fw_version, substr + 3, fw_level_len);
+		strscpy(adapter->fw_version, substr + 3,
+			sizeof(adapter->fw_version));
 	} else {
 		dev_info(dev, "FW substr extrapolated VPD buff\n");
 	}