drm/nouveau: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/nvkm: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch aims to suppress 29 missing-break-in-switch false positives.

Addresses-Coverity-ID: 1456891 ("Missing break in switch")
Addresses-Coverity-ID: 1324063 ("Missing break in switch")
Addresses-Coverity-ID: 1324063 ("Missing break in switch")
Addresses-Coverity-ID: 141432 ("Missing break in switch")
Addresses-Coverity-ID: 141433 ("Missing break in switch")
Addresses-Coverity-ID: 141434 ("Missing break in switch")
Addresses-Coverity-ID: 141435 ("Missing break in switch")
Addresses-Coverity-ID: 141436 ("Missing break in switch")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

drm/nouveau/mmu/nv04: implement vmm on top of new base

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

drm/nouveau/mmu/nv04-nv4x: move global vmm to nvkm_mmu

In a future commit, this will be constructed by common code.

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

drm/nouveau/mmu: convert to new-style nvkm_subdev

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

drm/nouveau/dma: convert user classes to new-style nvkm_object

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

drm/nouveau/dma: split user classes out from engine implementations

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