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/mvebu_db_armada8k_defconfig b/configs/mvebu_db_armada8k_defconfig
index 50cf3ed..22dc914 100644
--- a/configs/mvebu_db_armada8k_defconfig
+++ b/configs/mvebu_db_armada8k_defconfig
@@ -71,4 +71,8 @@
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_HOST_ETHER=y
+CONFIG_USB_ETHER_ASIX=y
+CONFIG_USB_ETHER_MCS7830=y
+CONFIG_USB_ETHER_RTL8152=y
+CONFIG_USB_ETHER_SMSC95XX=y
 CONFIG_SMBIOS_MANUFACTURER=""