configs: dra7xx_evm: enable eth driver model

Enable eth driver model for dra7xx_evm as cpsw supports
driver model.

This was already added with the commit 641b936fa5ba but with
commit bd7245849f7c to add fit support CONFIG_DM_ETH was missed.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/configs/dra7xx_evm_defconfig b/configs/dra7xx_evm_defconfig
index 44393d7..956b83e 100644
--- a/configs/dra7xx_evm_defconfig
+++ b/configs/dra7xx_evm_defconfig
@@ -62,3 +62,4 @@
 CONFIG_DM_REGULATOR=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_CMD_REGULATOR=y
+CONFIG_DM_ETH=y