ARM: rpi_b: detect board revision

Detect the board revision early during boot, and print the decoded
model name.

Eventually, this information can be used for tasks such as:
- Allowing/preventing USB device mode; some models have a USB device on-
  board so only host mode makes sense. Others connect the SoC directly
  to the USB connector, so device-mode might make sense.
- The on-board USB hub/Ethernet requires different GPIOs to enable it,
  although luckily the default appears to be fine so far.
- The compute module contains an on-board eMMC device, so we could store
  the environment there. Other models use an SD card and so don't support
  saving the environment (unless we store it in a file on the FAT boot
  partition...)

Set $fdtfile based on this information. At present, the mainline Linux
kernel doesn't contain a separate DTB for most models, but I hope that
will change soon.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
ARM: rpi: rename rpi_b to rpi

The U-Boot port runs on a variety of RPi models, not just the B. So,
rename the port to something slightly more generic.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
---
These two patches are based on "ARM: rpi_b: detect board revision" which
I sent recently.
ARM: rpi: support an environment

Enable ENV_IS_IN_FAT so that the environment can be stored persistently.
It's stored in the FAT partition that the RPi firmware requires. On most
RPis, this is on the SD card (which must be present in order for the
system to boot). On the CM this is on the built-in eMMC device.

Since we now have a persistent environment, there's no need to load
uEnv.txt at boot; we only did that to work around the lack of persistent
environment.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
LOCAL: ARM: rpi_b: add script to chain-load U-Boot over DHCP/TFTP

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
BROKEN: ARM: rpi: enable USB keyboard

This will allow the user to interact with U-Boot without a serial
console. Unfortunately this doesn't work at present; while USB Mass
Storage devices appear to work fine with U-Boot's DWC2 driver, USB
keyboard devices don't:-(

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Revert "BROKEN: ARM: rpi: enable USB keyboard"

This reverts commit 5504a530fe24b63489e49531f7d2a273b6f99fae.
ARM: rpi: only set usbethaddr on relevant systems

Model A and CM RPis don't have an on-board USB Ethernet device. Hence,
there's no point setting $usbethaddr based on the device fuses. Use the
model detection code to gate this. Note that the fuses are actually
programmed even on those devices though.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Revert "hush: fix segfault on syntax error"

This reverts commit 128059b926b3c34bbb364dcacd8d0511ff906be8.