arm: socfpga: misc: Probe ethernet GMAC from OF

The GMAC can now be probed from OF, so enable DM ethernet and remove the
old ad-hoc designware_initialize() invocation.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/socfpga_cyclone5_defconfig b/configs/socfpga_cyclone5_defconfig
index 992ce7e..75ed347 100644
--- a/configs/socfpga_cyclone5_defconfig
+++ b/configs/socfpga_cyclone5_defconfig
@@ -7,6 +7,7 @@
 # CONFIG_CMD_FLASH is not set
 CONFIG_OF_CONTROL=y
 CONFIG_SPI_FLASH=y
+CONFIG_DM_ETH=y
 CONFIG_NETDEVICES=y
 CONFIG_ETH_DESIGNWARE=y
 CONFIG_SPL_DM=y