fifo: fsync() returns EINVAL

fix #15288

Change-Id: Ic86bcec662c81cb04b743ec077cc8a2f3941f96e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3379
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

src/system/kernel/fs/fifo.cpp

@@ -922,7 +922,7 @@ fifo_free_cookie(fs_volume* _volume, fs_vnode* _node, void* _cookie)
 static status_t
 fifo_fsync(fs_volume* _volume, fs_vnode* _node)
 {
-	return B_OK;
+	return B_BAD_VALUE;
 }