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/tqma6dl_mba6_spi_defconfig b/configs/tqma6dl_mba6_spi_defconfig
index c2b18cf..955873b 100644
--- a/configs/tqma6dl_mba6_spi_defconfig
+++ b/configs/tqma6dl_mba6_spi_defconfig
@@ -39,4 +39,5 @@
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_HOST_ETHER=y
+CONFIG_USB_ETHER_SMSC95XX=y
 CONFIG_OF_LIBFDT=y