[beagleboard] TFTPBOOOT uImage

I know that U_Boot doesn't have built-in support for this with the
current omap3_beagle_config but I was wondering since U-Boot supports
USB-to-ethernet dongles, why isn't this included in the config so we
can easily test out new kernels?

I saw this was briefly discussed around a year ago but it seems like
it was never followed through. Couldn't/shouldn't this be added to at
least u-boot-c4??