drm/nouveau: use vmalloc for pgt allocation

Page tables on nv50 take 48kB, which can be hard to allocate in one piece.
Let's use vmalloc.
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: stable@vger.kernel.org [3.7+]
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/subdev/vm/base.c

@@ -365,7 +365,7 @@ nouveau_vm_create(struct nouveau_vmmgr *vmm, u64 offset, u64 length,
 	vm->fpde = offset >> (vmm->pgt_bits + 12);
 	vm->lpde = (offset + length - 1) >> (vmm->pgt_bits + 12);
 
-	vm->pgt  = kcalloc(vm->lpde - vm->fpde + 1, sizeof(*vm->pgt), GFP_KERNEL);
+	vm->pgt  = vzalloc((vm->lpde - vm->fpde + 1) * sizeof(*vm->pgt));
 	if (!vm->pgt) {
 		kfree(vm);
 		return -ENOMEM;
@@ -374,7 +374,7 @@ nouveau_vm_create(struct nouveau_vmmgr *vmm, u64 offset, u64 length,
 	ret = nouveau_mm_init(&vm->mm, mm_offset >> 12, mm_length >> 12,
 			      block >> 12);
 	if (ret) {
-		kfree(vm->pgt);
+		vfree(vm->pgt);
 		kfree(vm);
 		return ret;
 	}
@@ -450,7 +450,7 @@ nouveau_vm_del(struct nouveau_vm *vm)
 	}
 
 	nouveau_mm_fini(&vm->mm);
-	kfree(vm->pgt);
+	vfree(vm->pgt);
 	kfree(vm);
 }