usbcore: check device's LPM capability

Check device's LPM capability by examining the bmAttibutes field of the
USB2.0 Extension Descriptor.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>