usb: deal with broken config descriptors

Change usb_get_configuration() so that it is more tolerant to devices
with bad configuration descriptors (it'll make it ignore
configurations that fail to load).

Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>