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/UCP1020_defconfig b/configs/UCP1020_defconfig
index cada7bb..6718865 100644
--- a/configs/UCP1020_defconfig
+++ b/configs/UCP1020_defconfig
@@ -6,3 +6,5 @@
 CONFIG_AUTOBOOT_STOP_STR="\x1b"
 CONFIG_SPI_FLASH=y
 CONFIG_SYS_PROMPT="B$ "
+CONFIG_NETDEVICES=y
+CONFIG_E1000=y