arch/arm/src/lpc54xx: Completes basic packet transfer logic for Ethernet...

arch/arm/src/lpc54xx:  Completes basic packet transfer logic for Ethernet drivers.  Still some unfinished logic for IPv6 multicast logic and for various non-mainstream configurations.  But it is ready for tested.  configs/lpcxpresso-lpc54628:  Add a netnsh configuration that will be used to test the Ethernet driver.  Untested on initial commit.