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.

Change-Id: I94c7db85be3dfbd4d8065c0917ae9fdae6b2baa1
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>