Make the wusb_chid sysfs file match the ABI documentation.

Print all zeros if the WUSB host is stopped (instead of an empty file)
and end the file with a newline.
Signed-off-by: NDavid Vrabel <david.vrabel@csr.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>