tracing/syscalls: Annotate field-defining functions with __init

These two functions are called during kernel boot only.

Link: http://lkml.kernel.org/r/51258796.7020704@huawei.com



Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>