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/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
index 2fb84f9..5ac047d 100644
--- a/arch/arm/mach-exynos/Kconfig
+++ b/arch/arm/mach-exynos/Kconfig
@@ -21,6 +21,9 @@
 	imply CRC32_VERIFY
 	imply CMD_HASH
 	imply HASH_VERIFY
+	imply USB_ETHER_RTL8152
+	imply USB_ETHER_ASIX
+	imply USB_ETHER_SMSC95XX
 	help
 	  Samsung Exynos5 SoC family are based on ARM Cortex-A15 CPU (and
 	  Cortex-A7 CPU in big.LITTLE configuration). There are multiple SoCs