kernel: Refactor common _new_thread init code

We do a bit of the same stuff on all the arch's to setup a new thread.
So lets put that code in a common place so we unify it for everyone and
reduce some duplicated code.

Change-Id: Ic04121bfd6846aece16aa7ffd4382bdcdb6136e3
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
7 files changed