Add functions to retrieve data associated with an SCLP Store Data
entity. Automatically retrieve data for the "config" entity during
boot and make that data available to user-space via sysfs:

    /sys/firmware/sclp_sd/config/data
        Reading from this file will return config data contents.

    /sys/firmware/sclp_sd/config/reload
        Writing to this file will cause the latest version of data
        related to the config entity to be read from the SCLP interface.

Generate a KOBJ_CHANGE whenever new data is retrieved.
Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>