usb: net: migrate USB Ethernet adapters to Kconfig

This migrates ASIX, ASIX88179, MCS7830, RTL8152 and SMSC95XX to Kconfig.
Update defconfigs.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/nyan-big_defconfig b/configs/nyan-big_defconfig
index 996a675..29d918d 100644
--- a/configs/nyan-big_defconfig
+++ b/configs/nyan-big_defconfig
@@ -71,6 +71,7 @@
 CONFIG_G_DNL_VENDOR_NUM=0x0955
 CONFIG_G_DNL_PRODUCT_NUM=0x701a
 CONFIG_USB_HOST_ETHER=y
+CONFIG_USB_ETHER_ASIX=y
 CONFIG_DM_VIDEO=y
 CONFIG_DISPLAY=y
 CONFIG_VIDEO_TEGRA124=y