tracing/syscalls: Annotate raw_init function with __init

init_syscall_trace() can only be called during kernel bootup only, so we can
mark it and the functions it calls as __init.

Link: http://lkml.kernel.org/r/51528E89.6080508@huawei.com



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