board-dt-tegra*.c should support any board using Tegra when booted using
device tree. Instead of explicitly listing all the supported boards,
which requires a kernel change for each new board, list the supported SoC
model instead.

Note that the board files do currently have explicit support for setting
up each board's pinmux. However, it's fairly likely that at least the
basic devices on any new board will work just fine as set up by the boot-
loader, and the pinmux data should be moving into device tree soon anyway.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>