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/fennec-rk3288_defconfig b/configs/fennec-rk3288_defconfig
index 8615243..96a07de 100644
--- a/configs/fennec-rk3288_defconfig
+++ b/configs/fennec-rk3288_defconfig
@@ -75,6 +75,8 @@
 CONFIG_G_DNL_VENDOR_NUM=0x2207
 CONFIG_G_DNL_PRODUCT_NUM=0x320a
 CONFIG_USB_HOST_ETHER=y
+CONFIG_USB_ETHER_ASIX=y
+CONFIG_USB_ETHER_SMSC95XX=y
 CONFIG_USE_TINY_PRINTF=y
 CONFIG_CMD_DHRYSTONE=y
 CONFIG_ERRNO_STR=y