arm: mvebu: turris_omnia: Enable networking via ethernet switch

The Turris Omnia contains the Marvell 88E6176 ethernet switch. Add
config options and device tree to enable the support.

Signed-off-by: Marek Mojík <marek.mojik@nic.cz>
Signed-off-by: Marek Behún <kabel@kernel.org>
diff --git a/configs/turris_omnia_defconfig b/configs/turris_omnia_defconfig
index f045dd7..2914840 100644
--- a/configs/turris_omnia_defconfig
+++ b/configs/turris_omnia_defconfig
@@ -95,7 +95,9 @@
 CONFIG_SPI_FLASH_MTD=y
 CONFIG_PHY_MARVELL=y
 CONFIG_PHY_FIXED=y
+CONFIG_DM_DSA=y
 CONFIG_PHY_GIGE=y
+CONFIG_MV88E6XXX=y
 CONFIG_MVNETA=y
 CONFIG_MII=y
 CONFIG_MVMDIO=y