drivers: net: sandbox: add support for NET_LWIP

Make the sandbox mock ethernet driver (drivers/net/sandbox.c) compatible
with NET_LWIP by not relying on any of the structures or functions
defined in net-legacy.h. This is done by providing local definitions of
the various protocol structures (Ethernet, ARP, IPv4, ICMP). Drop the
stub driver that was introduced specifically for NET_LWIP
(drivers/net/sandbox-lwip.c).

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index a0a7890..69e4d94 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -358,7 +358,7 @@
 
 config ETH_SANDBOX
 	depends on SANDBOX
-	depends on NET
+	depends on NET || NET_LWIP
 	default y
 	bool "Sandbox: Mocked Ethernet driver"
 	help
@@ -367,17 +367,6 @@
 
 	  This driver is particularly useful in the test/dm/eth.c tests
 
-config ETH_SANDBOX_LWIP
-	depends on SANDBOX
-	depends on NET_LWIP
-	default y
-	bool "Sandbox: Mocked Ethernet driver (for NET_LWIP)"
-	help
-	  This driver is meant as a replacement for ETH_SANDBOX when
-	  the network stack is NET_LWIP rather than NET. It currently
-	  does nothing, i.e. it drops the sent packets and never receives
-	  data.
-
 config ETH_SANDBOX_RAW
 	depends on SANDBOX
 	depends on NET