Add support to return serial number to OSTC devices

This data isn't per dive, but it makes sense to return it here as a
string (we already return it as unsigned int in the devinfo event after
opening the device).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

src/hw_ostc_parser.c

@@ -541,6 +541,10 @@ hw_ostc_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, unsigned
 				string->desc = "FW Version";
 				snprintf(buf, BUFLEN, "%0u.%0u", data[layout->fw_version], data[layout->fw_version + 1]);
 				break;
+			case 3: /* serial */
+				string->desc = "Serial";
+				snprintf(buf, BUFLEN, "%u", parser->serial);
+				break;
 			default:
 				return DC_STATUS_UNSUPPORTED;
 			}