xhci: A default implementation for Ux timeout calculation and tier policy check
As best case, a host controller should support U0 to U1 switching for
the devices connected below any tier of hub level supported by usb
specification. Therefore xhci_check_tier_policy should always return
success as default implementation.
A host should be able to issue LGO_Ux after the timeout calculated as
per definition of system exit latency defined in C.1.5.2. Therefore
xhci_calculate_ux_timeout returns ux_params.sel as the default
implementation.
Use default calculation in absence of any vendor specific limitations.