usb: net: migrate CONFIG_USB_HOST_ETHER to Kconfig

CONFIG_USB_HOST_ETHER is the framework that the drivers are dependent on
USB_HOST_ETHER. Use this as a menu and move the existing LAN75XX and
LAN78XX options under new menu. Finally update the defconfigs that need
CONFIG_USB_HOST_ETHER.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/miqi-rk3288_defconfig b/configs/miqi-rk3288_defconfig
index b669c8c..eb5ff7a 100644
--- a/configs/miqi-rk3288_defconfig
+++ b/configs/miqi-rk3288_defconfig
@@ -74,6 +74,7 @@
 CONFIG_G_DNL_MANUFACTURER="Rockchip"
 CONFIG_G_DNL_VENDOR_NUM=0x2207
 CONFIG_G_DNL_PRODUCT_NUM=0x320a
+CONFIG_USB_HOST_ETHER=y
 CONFIG_DM_VIDEO=y
 CONFIG_DISPLAY=y
 CONFIG_VIDEO_ROCKCHIP=y