drm/nouveau: prepare for reporting channel owner

- record channel owner process name
- add some helpers for accessing this information
- let nouveau_enum hold additional value (will be needed in the next patch)

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
7 files changed