ANDROID: fork: Export task_newtask tracepoint

android_rvh_sched_fork() and android_rvh_sched_fork_init()
already let us register probes during fork(), but those are
invoked *before* the new task is added to the tasklist, which
can lead to some undesired races when a module is trying to
initialize vendor-specific task_struct fields.

Export the task_newtask tracepoint to register probes to run
during fork() but *after* the task has been inserted into the
tasklist.

Bug: 192873984
Signed-off-by: Jing-Ting Wu <Jing-Ting.Wu@mediatek.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Change-Id: Ifef14819264385b5e955a5966b4e4f66d50da5e3