usbcore: Bug fix: system can't suspend with USB3.0 device connected to USB3.0 hub

This patch clear PORT_POWER when suspend a USB3.0 device behind a USB3.0
external hub, so the system can suspend and resume.

Note USB3.0 device may not work after system resume and this is a temporary
workaround. The correct fix will be in future patches.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>