ARM: embestmx6boards: convert mars/riot boards to DM_USB

Convert the marsboard/riotboard to use DM_USB.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Cc: "Eric BĂ©nard" <eric@eukrea.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/configs/riotboard_defconfig b/configs/riotboard_defconfig
index 4f86a08..1e5dc39 100644
--- a/configs/riotboard_defconfig
+++ b/configs/riotboard_defconfig
@@ -59,6 +59,7 @@
 CONFIG_DM_THERMAL=y
 CONFIG_IMX_THERMAL=y
 CONFIG_USB=y
+CONFIG_DM_USB=y
 CONFIG_USB_HOST_ETHER=y
 CONFIG_USB_ETHER_ASIX=y
 CONFIG_DM_VIDEO=y