Some USB ports can support host and device operation. We add the dr_mode
property (as found in Freescale) for this.

One USB port has a 'legacy mode', left over from the days of pre-Tegra
chips. I don't believe this is actually used, except that we must know
to turn this off in the driver.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Acked-by: NStephen Warren <swarren@wwwdotorg.org>
Signed-off-by: NOlof Johansson <olof@lixom.net>

For now they are a minimal binding. It needs to be amended with
vendor-specific settings for phy setup and link tuning, etc.

v2: Added bindings specification and phy_type properties
Signed-off-by: NOlof Johansson <olof@lixom.net>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NStephen Warren <swarren@nvidia.com>