Add new vendor specific attribute 769 in TCP/IP Interface Object that holds the maximum DHCP-DISCOVER re-transmission rate

Add new vendor specific attribute 769 to the TCP/IP Interface Object that holds the maximum DHCP-DISCOVER re-transmission rate.

This new attribute serves as an interface to the TCP-Stack'S DHCP client implementation.
It provides a means to configure the maximum DHCP DISCOVER re-transmission rate.

Data type: USINT (8 bit)
Range: 4 - 60 seconds,
default: 60 seconds

The attribute shall be stored in remanent data.
The attribute shall be settable and gettable from the network and host.