sandbox: eth: Add network support to sandbox

Add basic network support to sandbox which includes a network driver.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/sandbox/README.sandbox b/board/sandbox/README.sandbox
index 3c0df17..c1f5f7e 100644
--- a/board/sandbox/README.sandbox
+++ b/board/sandbox/README.sandbox
@@ -173,16 +173,16 @@
 - Chrome OS EC
 - GPIO
 - Host filesystem (access files on the host from within U-Boot)
+- I2C
 - Keyboard (Chrome OS)
 - LCD
+- Network
 - Serial (for console only)
 - Sound (incomplete - see sandbox_sdl_sound_init() for details)
 - SPI
 - SPI flash
 - TPM (Trusted Platform Module)
 
-Notable omissions are networking and I2C.
-
 A wide range of commands is implemented. Filesystems which use a block
 device are supported.