Hardware link powermanagement in usb2 is a per-port capability.
Previously support for hw lpm was enabled for all ports if any usb2 port supported it.

Now instead cache the capability values and check them for each port individually
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NSarah Sharp <sarah.a.sharp@linux.intel.com>