s390: vfio-ap: sysfs interface to view matrix mdev matrix

Provides a sysfs interface to view the AP matrix configured for the
mediated matrix device.

The relevant sysfs structures are:

/sys/devices/vfio_ap/matrix/
...... [mdev_supported_types]
......... [vfio_ap-passthrough]
............ [devices]
...............[$uuid]
.................. matrix

To view the matrix configured for the mediated matrix device,
print the matrix file:

	cat matrix

Below are examples of the output from the above command:

Example 1: Adapters and domains assigned
	Assignments:
		Adapters 5 and 6
		Domains 4 and 71 (0x47)

	Output
		05.0004
		05.0047
		06.0004
	06.0047

Examples 2: Only adapters assigned
	Assignments:
		Adapters 5 and 6

	Output:
		05.
		06.

Examples 3: Only domains assigned
	Assignments:
		Domains 4 and 71 (0x47)

	Output:
		.0004
		.0047

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Tested-by: Michael Mueller <mimu@linux.ibm.com>
Tested-by: Farhan Ali <alifm@linux.ibm.com>
Tested-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20180925231641.4954-10-akrowiak@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>