drm/nouveau: move nvxx_* definitions to nouveau_drv.h

drm/nouveau: move nvxx_* definitions to nouveau_drv.h

These are some dodgy "convenience" macros for the DRM driver to peek
into NVKM state.  They're still used in a few places, but don't belong
in nvif/device.h in any case.

Move them to nouveau_drv.h, and modify callers to pass a nouveau_drm
instead of an nvif_device.

v2:
- use drm->nvkm pointer for nvxx_*() macros, removing some void*
v3:
- add some explanation of the nvxx_*() macros

Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240726043828.58966-28-bskeggs@nvidia.com