usb: dwc3: debugfs: Properly print/set link state for HS

Highspeed device and below has different state names than superspeed and
higher. Add proper checks and printouts of link states for highspeed and
below.

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>