uboot-phytec

test: dm: eth: Add tests for the eth dm implementation

Add a test for the eth uclass using the sandbox eth driver. Verify basic
functionality of the network stack / eth uclass by exercising the ping
function.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>