xhci: add definitions for all port link states

Add definitions for all port link states defined in xhci
specification for PORTSC register.

Will be needed for human readable port status tracing

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>