Disable commands which are only used by cros_config for fallback

Disable the following commands, which are only used by cros_config to
get the data on pre-unibuild devices:

- mosys psu type
- mosys platform brand
- mosys platform customization

These will become visible on pre-unibuild devices by setting the
environment variable I_AM_CROS_CONFIG=1 (which cros_config does now).

BUG=b:184257014
TEST=on samus:
     # mosys psu type
     Command not supported on this platform
     # I_AM_CROS_CONFIG=1 mosys psu type
     battery

Change-Id: I3c5c092e48a8435a93531fbae2b178dd4d721cef
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/mosys/+/2802848
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
4 files changed