Revert "drm/nouveau/firmware: Fix SG_DEBUG error with nvkm_firmware_ctor()"

This reverts commit 52a6947b.

This causes loading failures in
[    0.367379] nouveau 0000:01:00.0: NVIDIA GP104 (134000a1)
[    0.474499] nouveau 0000:01:00.0: bios: version 86.04.50.80.13
[    0.474620] nouveau 0000:01:00.0: pmu: firmware unavailable
[    0.474977] nouveau 0000:01:00.0: fb: 8192 MiB GDDR5
[    0.484371] nouveau 0000:01:00.0: sec2(acr): mbox 00000001 00000000
[    0.484377] nouveau 0000:01:00.0: sec2(acr):load: boot failed: -5
[    0.484379] nouveau 0000:01:00.0: acr: init failed, -5
[    0.484466] nouveau 0000:01:00.0: init failed with -5
[    0.484468] nouveau: DRM-master:00000000:00000080: init failed with -5
[    0.484470] nouveau 0000:01:00.0: DRM-master: Device allocation failed: -5
[    0.485078] nouveau 0000:01:00.0: probe with driver nouveau failed with error -50

I tried tracking it down but ran out of time this week, will revisit next week.
Reported-by: Dan Moulding <dan@danm.net>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nvkm/core/firmware.c

@@ -205,9 +205,7 @@ nvkm_firmware_dtor(struct nvkm_firmware *fw)
 		break;
 	case NVKM_FIRMWARE_IMG_DMA:
 		nvkm_memory_unref(&memory);
-		dma_unmap_single(fw->device->dev, fw->phys, sg_dma_len(&fw->mem.sgl),
-				 DMA_TO_DEVICE);
-		kfree(fw->img);
+		dma_free_coherent(fw->device->dev, sg_dma_len(&fw->mem.sgl), fw->img, fw->phys);
 		break;
 	case NVKM_FIRMWARE_IMG_SGT:
 		nvkm_memory_unref(&memory);
@@ -237,17 +235,14 @@ nvkm_firmware_ctor(const struct nvkm_firmware_func *func, const char *name,
 		fw->img = kmemdup(src, fw->len, GFP_KERNEL);
 		break;
 	case NVKM_FIRMWARE_IMG_DMA: {
-		len = ALIGN(fw->len, PAGE_SIZE);
+		dma_addr_t addr;
 
-		fw->img = kmalloc(len, GFP_KERNEL);
-		if (!fw->img)
-			return -ENOMEM;
+		len = ALIGN(fw->len, PAGE_SIZE);
 
+		fw->img = dma_alloc_coherent(fw->device->dev, len, &addr, GFP_KERNEL);
+		if (fw->img) {
 			memcpy(fw->img, src, fw->len);
-		fw->phys = dma_map_single(fw->device->dev, fw->img, len, DMA_TO_DEVICE);
-		if (dma_mapping_error(fw->device->dev, fw->phys)) {
-			kfree(fw->img);
-			return -EFAULT;
+			fw->phys = addr;
 		}
 
 		sg_init_one(&fw->mem.sgl, fw->img, len);