usb: expose usb port's pm qos flags to user space

This patch is to expose usb port's pm qos flags(pm_qos_no_power_off,
pm_qos_remote_wakeup) to user space. User can set pm_qos_no_power_off
flag to prohibit the port from being powered off.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>