s390/hypfs: Add diagnose 0c support

s390/hypfs: Add diagnose 0c support

With this feature, you can read the CPU performance metrics provided by the
z/VM diagnose 0C. This then allows to get the management time for each
online CPU of the guest where the diagnose is executed.

The new debugfs file /sys/kernel/debug/s390_hypfs/diag_0c exports the
diag0C binary data to user space via an open/read/close interface.

The binary data consists out of a header structure followed by an
array that contains the diagnose 0c data for each online CPU.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>