[PATCH] s390 (2/7): common i/o layer.

[PATCH] s390 (2/7): common i/o layer.

 - Remove atomic_read hack to test for presence of ccw device directory.
 - Add dummy release function to channel path object and cu3088 group devices.
 - Don't rely on the chaining bit of the channel report word.
 - Don't call schedule while holding a lock in read_dev_chars/read_conf_data.