drm/nouveau/fb: fix null derefs in nv49 and nv4e init

Commit dceef5d8 (drm/nouveau/fb: initialise vram controller as pfb
sub-object) moved some code around and introduced these null derefs.
pfb->ram is set to the new ram object outside of this ctor.
Reported-by: Ronald Uitermark <ronald645@gmail.com>
Tested-by: Ronald Uitermark <ronald645@gmail.com>
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv49.c

@@ -40,15 +40,15 @@ nv49_ram_create(struct nouveau_object *parent, struct nouveau_object *engine,
 		return ret;
 
 	switch (pfb914 & 0x00000003) {
-	case 0x00000000: pfb->ram->type = NV_MEM_TYPE_DDR1; break;
-	case 0x00000001: pfb->ram->type = NV_MEM_TYPE_DDR2; break;
-	case 0x00000002: pfb->ram->type = NV_MEM_TYPE_GDDR3; break;
+	case 0x00000000: ram->type = NV_MEM_TYPE_DDR1; break;
+	case 0x00000001: ram->type = NV_MEM_TYPE_DDR2; break;
+	case 0x00000002: ram->type = NV_MEM_TYPE_GDDR3; break;
 	case 0x00000003: break;
 	}
 
-	pfb->ram->size  =  nv_rd32(pfb, 0x10020c) & 0xff000000;
-	pfb->ram->parts = (nv_rd32(pfb, 0x100200) & 0x00000003) + 1;
-	pfb->ram->tags  =  nv_rd32(pfb, 0x100320);
+	ram->size  =  nv_rd32(pfb, 0x10020c) & 0xff000000;
+	ram->parts = (nv_rd32(pfb, 0x100200) & 0x00000003) + 1;
+	ram->tags  =  nv_rd32(pfb, 0x100320);
 	return 0;
 }
 

drivers/gpu/drm/nouveau/core/subdev/fb/ramnv4e.c

@@ -38,8 +38,8 @@ nv4e_ram_create(struct nouveau_object *parent, struct nouveau_object *engine,
 	if (ret)
 		return ret;
 
-	pfb->ram->size = nv_rd32(pfb, 0x10020c) & 0xff000000;
-	pfb->ram->type = NV_MEM_TYPE_STOLEN;
+	ram->size = nv_rd32(pfb, 0x10020c) & 0xff000000;
+	ram->type = NV_MEM_TYPE_STOLEN;
 	return 0;
 }