usb: core: hub: Enable/disable U1/U2 in configured state

SET_FEATURE(U1/U2_ENABLE) and CLEAR_FEATURE(U1/U2) only apply while the
device is in configured state. Add proper check in usb_disable_lpm() and
usb_enable_lpm() for enabling/disabling device-initiated U1/U2.

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>