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/arch/Kconfig b/arch/Kconfig
index c2b4070..0b12ed9 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -116,6 +116,8 @@
 	imply CMD_SF_TEST
 	imply CMD_ZBOOT
 	imply USB_HOST_ETHER
+	imply USB_ETHER_ASIX
+	imply USB_ETHER_SMSC95XX
 
 config XTENSA
 	bool "Xtensa architecture"