Network: Move unused etharp definitions to ARP component

[Courtney3141]

This PR removes unused Ethernet/ARP constants to the [depreciated] ARP component, which it was agreed upon to keep in the sDDF repo for the time being.

[wom-bat]

Does it make sense to have a header file containing all the ethernet packet types somewhere and use that, rather than insert the definitions into a C file?

[Courtney3141]

@wom-bat I made this PR as we are in the process of merging Kuba's work on the vswitch #685 where he creates a specific header file for the ethernet header, along with other relevant definitions. In particular, I was going to suggest to him to move the eth-type/eth-arp definitions into his new header file, but then I noticed that they were not used in the codebase at all, with the exception of the arp component.

My plan was to remove them entirely, however, since we have previously agreed to keep the ARP component around (even though it is currently completely depreciated, and will no longer build/doesn't have sdfgen support), I moved the definitions there. This was additionally motivated by the fact we had other relevant ARP related network definitions there which are solely used by the ARP component.

[Courtney3141]

See @JDuchniewicz 's new header file which should be merged shortly

[wom-bat]

I was thinking of something more like /usr/include/net/ethernet.h on POSIX systems

[Courtney3141]

Are you suggesting a name change for @JDuchniewicz 's PR? Or creating a different file with the ARP specific definitions? We do something similar for the firewall.

A name change seems reasonable, but I am tentative to put any time into moving around the ARP component definitions for the time being, since the component can't really be used in it's current form.

[Ivan-Velickovic]

I was thinking of something more like /usr/include/net/ethernet.h on POSIX systems

I agree, we should just have one header file for users of the ethernet sub-system.