drm/nouveau: uapi: fix kerneldoc warnings

drm/nouveau: uapi: fix kerneldoc warnings

As of commit b77fdd6a48e6 ("scripts/kernel-doc: restore warning for
Excess struct/union"), we see the following warnings when running 'make
htmldocs':

  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_OP_MAP' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_OP_UNMAP' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_SPARSE' description in 'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:336: warning: Excess struct member 'DRM_NOUVEAU_VM_BIND_RUN_ASYNC' description in 'drm_nouveau_vm_bind'

The problem is that these values are #define constants, but had kerneldoc
comments attached to them as if they were actual struct members.

There are a number of ways we could fix this, but I chose to draw
inspiration from include/uapi/drm/i915_drm.h, which pulls them into the
corresponding kerneldoc comment for the struct member that they are
intended to be used with.

To keep the diff readable, there are a number of things I _didn't_ do in
this patch, but which we should also consider:

- This is pretty good documentation, but it ends up in gpu/driver-uapi,
  which is part of subsystem-apis/ when it really ought to display under
  userspace-api/ (the "Linux kernel user-space API guide" book of the
  documentation).

- More generally, we might want a warning if include/uapi/ files are
  kerneldoc'd outside userspace-api/.

- I'd consider it cleaner if the #defines appeared between the kerneldoc
  for the member and the member itself (which is something other DRM-
  related UAPI docs do).

- The %IDENTIFIER kerneldoc syntax is intended for "constants", and is
  more appropriate in this context than ``IDENTIFIER`` or &IDENTIFIER.
  The DRM docs aren't very consistent on this.

Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231225065145.3060754-1-vegard.nossum@oracle.com