net: lwip: add DHCP support and dhcp commmand

Add what it takes to enable NETDEVICES with NET_LWIP and enable DHCP as
well as the dhcp command. CMD_TFTPBOOT is selected by BOOTMETH_EFI due
to this code having an implicit dependency on do_tftpb().

Note that PXE is likely non-fonctional with NET_LWIP (or at least not
100% functional) because DHCP option 209 is not supported by the lwIP
library. Therefore, BOOTP_PXE_DHCP_OPTION cannot be enabled.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/common/board_r.c b/common/board_r.c
index 1acad06..e5f33f4 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -484,7 +484,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_CMD_NET
+#if defined(CONFIG_CMD_NET)
 static int initr_net(void)
 {
 	puts("Net:   ");
@@ -749,7 +749,7 @@
 #ifdef CONFIG_PCI_ENDPOINT
 	pci_ep_init,
 #endif
-#ifdef CONFIG_CMD_NET
+#if defined(CONFIG_CMD_NET)
 	INIT_FUNC_WATCHDOG_RESET
 	initr_net,
 #endif