The generic power-domain framework has been updated to allow devices
that require more than one power-domain to create a new device for
each power-domain required and then link these new power-domain
devices to the consumer device.
Update the Tegra xHCI driver to use the new APIs provided by the
generic power-domain framework so we can use the generic power-domain
framework for managing the xHCI controllers power-domains. Please
note that to maintain backward compatibility with older device-tree
blobs these new generic power-domain APIs are only used if the
'power-domains' property is present and otherwise we fall back to
using the legacy Tegra APIs for managing the power-domains.