xhci: move usb2 get port status link resume handling to its own function

Refactoring, no functional changes.

But worth mentioning that checking for port link resume state is now behind
a additional port power check.

This is fine as ports can't be in resume state if port power bit is not
set.

xhci spec section 4.19.1.1.6 figure 34 shows that port power bit must be
set for all 'Enable' substates, including U0,U1,U2,U3 (suspended), Resume,
and RExit states.

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