usb: allow lpm (en/dis)able only if device is atleast in default state

When a USB device is disconnected, usb_unbind_interface is called, which
tries to enable and disable LPM. usb_enable_lpm also try to send a
control command SET SEL to the device.
Since device is already disconnected, therefore it does not make sense
to execute usb_(en/dis)able_lpm.
This patch returns from usb_(en/dis)able_lpm, if device was not in
default state atleast.

Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Tested-by: Aymen Bouattay <aymen.bouattay@st.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>