drm/nouveau/sw: rename from software (no binary change)

Shorter device name, make consistent with our engine enums.

The namespace of NVKM is being changed to nvkm_ instead of nouveau_,
which will be used for the DRM part of the driver.  This is being
done in order to make it very clear as to what part of the driver a
given symbol belongs to, and as a minor step towards splitting the
DRM driver out to be able to stand on its own (for virt).

Because there's already a large amount of churn here anyway, this is
as good a time as any to also switch to NVIDIA's device and chipset
naming to ease collaboration with them.

A comparison of objdump disassemblies proves no code changes.

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

drivers/gpu/drm/nouveau/include/nvif/device.h

@@ -53,7 +53,7 @@ void nvif_device_ref(struct nvif_device *, struct nvif_device **);
 #include <engine/device.h>
 #include <engine/fifo.h>
 #include <engine/gr.h>
-#include <engine/software.h>
+#include <engine/sw.h>
 
 #define nvkm_fifo(a) nouveau_fifo(nvkm_device(a))
 #define nvkm_fifo_chan(a) ((struct nouveau_fifo_chan *)nvkm_object(a))