arm: tegra: initial support for apalis t30

This patch adds board support for the Toradex Apalis T30 a computer on
module which can be used on different carrier boards.

For the sake of ease of use we do not distinguish between different
carrier boards for now as the base module features are deemed
sufficient enough for regular booting.

The following functionality is working so far:
- eMMC boot and environment storage
- Gigabit Ethernet (once Thierry's PCIe as well as my E1000 resp. i210
  fixes hit mainline)
- MMC/SD cards (both 8-bit as well as 4-bit slot)
- USB client/host (dual role port as client e.g. for DFU/UMS, other two
  ports as host)

Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>