bootstd: ethernet: Add a bootdev driver

Add a bootdev driver for Ethernet. It can use the PXE boot mechanism to
locate a file, added later.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/net/Makefile b/net/Makefile
index fb3eba8..6c81250 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -12,6 +12,7 @@
 obj-$(CONFIG_DM_DSA)   += dsa-uclass.o
 ifdef CONFIG_DM_ETH
 obj-$(CONFIG_NET)      += eth-uclass.o
+obj-$(CONFIG_$(SPL_TPL_)BOOTDEV_ETH) += eth_bootdev.o
 else
 obj-$(CONFIG_NET)      += eth_legacy.o
 endif