drm/nouveau: replace ffsll with __ffs64

The ffsll function is a lot slower than the __ffs64 built-in which
compiles to a single instruction on 64-bit. It's also nice to avoid
custom versions of standard functions. Note that __ffs == ffs - 1.
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/core/parent.c

@@ -49,7 +49,7 @@ nouveau_parent_sclass(struct nouveau_object *parent, u16 handle,
 
 	mask = nv_parent(parent)->engine;
 	while (mask) {
-		int i = ffsll(mask) - 1;
+		int i = __ffs64(mask);
 
 		if (nv_iclass(parent, NV_CLIENT_CLASS))
 			engine = nv_engine(nv_client(parent)->device);

drivers/gpu/drm/nouveau/nouveau_abi16.c

@@ -270,8 +270,8 @@ nouveau_abi16_ioctl_channel_alloc(ABI16_IOCTL_ARGS)
 		return nouveau_abi16_put(abi16, -EINVAL);
 
 	/* allocate "abi16 channel" data and make up a handle for it */
-	init->channel = ffsll(~abi16->handles);
-	if (!init->channel--)
+	init->channel = __ffs64(~abi16->handles);
+	if (~abi16->handles == 0)
 		return nouveau_abi16_put(abi16, -ENOSPC);
 
 	chan = kzalloc(sizeof(*chan), GFP_KERNEL);