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/theadorable-x86-conga-qa3-e3845_defconfig b/configs/theadorable-x86-conga-qa3-e3845_defconfig
index 569e750..4c9492c 100644
--- a/configs/theadorable-x86-conga-qa3-e3845_defconfig
+++ b/configs/theadorable-x86-conga-qa3-e3845_defconfig
@@ -49,6 +49,8 @@
 CONFIG_E1000=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_KEYBOARD=y
+CONFIG_USB_ETHER_MCS7830=y
+CONFIG_USB_ETHER_RTL8152=y
 CONFIG_FRAMEBUFFER_SET_VESA_MODE=y
 CONFIG_FRAMEBUFFER_VESA_MODE_114=y
 CONFIG_CONSOLE_SCROLL_LINES=5