dm: arm: rpi: Use driver model for Ethernet

Enable CONFIG_DM_ETH so that driver model is used for the USB Ethernet
device.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/rpi_3_32b_defconfig b/configs/rpi_3_32b_defconfig
index 8db0a58..306d54f 100644
--- a/configs/rpi_3_32b_defconfig
+++ b/configs/rpi_3_32b_defconfig
@@ -17,6 +17,7 @@
 CONFIG_OF_EMBED=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_BCM2835=y
+CONFIG_DM_ETH=y
 # CONFIG_REQUIRE_SERIAL_CONSOLE is not set
 CONFIG_USB=y
 CONFIG_DM_USB=y