ARM: tegra: enable USB device mode and UMS on some boards

For each of Jetson TK1, Venice2, and Beaver:

- Enable the first USB controller in DT, and describe its configuration.

- Enable USB device/gadget support. This allows the user to type e.g.
  "ums 0 mmc 0" at the command-line to cause U-Boot to act a USB device
  implementing the USB Mass Storage protocol, and expose MMC device 0
  that way.

This allows a host PC to mount the Tegra device's MMC, partition it, and
install a filesystem on it.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
v3: Use assigned USB device ID rather than random made-up value.
v2: Add missing tegra-common-ums.h
HACK: ARM: tegra: enable DFU too

FIXME: This should likely be in a separate tegra-common-dfu.h.

Signed-off-by: Stephen Warren <swarren@nvidia.com>