net: Move CONFIG_E1000 options to Kconfig

Move config for the E1000 Ethernet driver to Kconfig and tidy up affected
boards.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/ls1021atwr_nor_defconfig b/configs/ls1021atwr_nor_defconfig
index 939be78..0a4b3ea 100644
--- a/configs/ls1021atwr_nor_defconfig
+++ b/configs/ls1021atwr_nor_defconfig
@@ -1,3 +1,5 @@
 CONFIG_ARM=y
 CONFIG_TARGET_LS1021ATWR=y
 # CONFIG_CMD_SETEXPR is not set
+CONFIG_NETDEVICES=y
+CONFIG_E1000=y