USB VBUS regulators are now specified with the vbus-supply property
instead of nvidia,vbus-gpio, so remove the obsolete properties.

The equivalent vbus-supply properties were already added in patch
"ARM: tegra: update device trees for USB binding rework".
Signed-off-by: NMikko Perttunen <mperttunen@nvidia.com>
Acked-by: NStephen Warren <swarren@nvidia.com>
Reviewed-by: NStephen Warren <swarren@nvidia.com>
Tested-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>