Xe DRM client usage stats implementation

The drm/xe driver implements the DRM client usage stats specification as documented in DRM client usage stats.

Example of the output showing the implemented key value pairs and entirety of the currently possible format options:

pos:    0
flags:  0100002
mnt_id: 26
ino:    685
drm-driver:     xe
drm-client-id:  3
drm-pdev:       0000:03:00.0
drm-total-system:       0
drm-shared-system:      0
drm-active-system:      0
drm-resident-system:    0
drm-purgeable-system:   0
drm-total-gtt:  192 KiB
drm-shared-gtt: 0
drm-active-gtt: 0
drm-resident-gtt:       192 KiB
drm-total-vram0:        23992 KiB
drm-shared-vram0:       16 MiB
drm-active-vram0:       0
drm-resident-vram0:     23992 KiB
drm-total-stolen:       0
drm-shared-stolen:      0
drm-active-stolen:      0
drm-resident-stolen:    0
drm-cycles-rcs: 28257900
drm-total-cycles-rcs:   7655183225
drm-cycles-bcs: 0
drm-total-cycles-bcs:   7655183225
drm-cycles-vcs: 0
drm-total-cycles-vcs:   7655183225
drm-engine-capacity-vcs:        2
drm-cycles-vecs:        0
drm-total-cycles-vecs:  7655183225
drm-engine-capacity-vecs:       2
drm-cycles-ccs: 0
drm-total-cycles-ccs:   7655183225
drm-engine-capacity-ccs:        4

Possible drm-cycles- key names are: rcs, ccs, bcs, vcs, vecs and “other”.