arm: tegra: dts: Mark USB1 as an OTG port on Seaboard

The USB1 port on Tegra2 supports operation in host or device modes. On
Seaboard this is possible, so mark the port as OTG.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Olof Johansson <olof@lixom.net>