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/arch/sandbox/Kconfig b/arch/sandbox/Kconfig
index 477a20a..e7f55fa 100644
--- a/arch/sandbox/Kconfig
+++ b/arch/sandbox/Kconfig
@@ -41,4 +41,13 @@
 	  used on some devices to allow the CPU to communicate with its
 	  peripherals.
 
+config NET
+	default y
+
+config NETDEVICES
+	default y
+
+config DM_ETH
+	default y
+
 endmenu