vfio/mdev: consolidate all the name sysfs into the core code

Every driver just emits a static string, simply add a field to the
mdev_type for the driver to fill out or fall back to the sysfs name and
provide a standard sysfs show function.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Link: https://lore.kernel.org/r/20220923092652.100656-12-hch@lst.de
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

include/linux/mdev.h

@@ -26,6 +26,7 @@ struct mdev_device {
 struct mdev_type {
 	/* set by the driver before calling mdev_register parent: */
 	const char *sysfs_name;
+	const char *pretty_name;
 
 	/* set by the core, can be used drivers */
 	struct mdev_parent *parent;