bnxt_en: Extend maximum length of version string by 1 byte

This corrects an out-by-one error in the maximum length of the package
version string. The size argument of snprintf includes space for the
trailing '\0' byte, so there is no need to allow extra space for it by
reducing the value of the size argument by 1.

Found by inspection.
Compile tested only.

Signed-off-by: Simon Horman <horms@kernel.org>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20240813-bnxt-str-v2-1-872050a157e7@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c

@@ -4161,7 +4161,7 @@ static void bnxt_get_pkgver(struct net_device *dev)
 
 	if (!bnxt_get_pkginfo(dev, buf, sizeof(buf))) {
 		len = strlen(bp->fw_ver_str);
-		snprintf(bp->fw_ver_str + len, FW_VER_STR_LEN - len - 1,
+		snprintf(bp->fw_ver_str + len, FW_VER_STR_LEN - len,
 			 "/pkg %s", buf);
 	}
 }