arm: tegra: dts: Add legacy mode support to Tegra2x USB1 port

Tegra's USB1 port supports legacy mode, so mark it as such. Even if we
don't use it, we must turn it off in the driver.

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