usbip: vhci_hcd: clear just the USB_PORT_STAT_POWER bit

Upstream commit 1c9de5bf4286 ("usbip: vhci-hcd: Add USB3 SuperSpeed
support")

vhci_hcd clears all the bits port_status bits instead of clearing
just the USB_PORT_STAT_POWER bit when it handles ClearPortFeature:
USB_PORT_FEAT_POWER. This causes vhci_hcd attach to fail in a bad
state, leaving device unusable by the client. The device is still
attached and however client can't use it.

The problem was fixed as part of larger change to add  USB3 Super
Speed support. This patch backports just the change to clear the
USB_PORT_STAT_POWER.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>