USB: cdc-wdm: fix misuse of logical operation in place of bitop

CC: Greg Kroah-Hartman <gregkh@suse.de>
CC: Oliver Neukum <oliver@neukum.org>
CC: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>