DWC2: add host driver from Oleksandr's branch

swarren changelog:
* Fixed prototype of usb_lowlevel_init() to match upstream change.

TODO:
* Rename dwc -> dwc2

Signed-off-by: Oleksandr Tymoshenko <gonzo@bluezbox.com>
Signed-off-by: Stephen Warren <swarren@wwdotorg.org>
DWC2: fix unused variables

TODO: Squash into previous commit.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
DWC2: rename from DWC

TODO: Squash into previous commit.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
ARM: rpi_b: enable USB features in config

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
ARM: rpi_b: handle DWC->DWC2 rename

TODO: Squash into previous commit

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
HACK: SMSC95XX: hard-code Ethernet address

TODO: get this from firmware instead

Signed-off-by: Oleksandr Tymoshenko <gonzo@bluezbox.com>
[swarren: extracted from a larger patch]
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
ARM: rpi_b: hack in bootcmd from Tegra

TODO:
a) Split this out into common file to share with Tegra and other SoCs.
b) Enable all the syslinux/pxe stuff too.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
ARM: rpi_b: load /uEnv.txt from MMC at startup

The Pi has no flash to store an environment in the usual fashion. However,
the user may wish to customize the environment. We know that the SD card
must be present, since that's where the boot ROM has loaded U-Boot from.
So, load uEnv.txt from there early during boot. This allows the user to
e.g. customize boot_targets, in order to automatically select network
boot.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>