drm/nouveau/disp: add common channel class handling

Replaces a bunch of unnecessarily duplicated boilerplate in per-chipset
code with a simpler, common, implementation.

Channel "awaken" notify code is completely gone for now. KMS has never
made use of it so far, and event notify handling is about to be changed
in general anyway.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drm/nouveau/nvif: give every object a human-readable identifier

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/kms/nv50-: initial overlay support

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/kms/nv50-: split each resource type into their own source files

There should be no code changes here, just shuffling stuff around.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>