This adds unit test for microkernel private mailboxes.
The code piggybacks to the public mailbox test (by
including the same source files), so any updates to
the test will be applied to both.
Note that the prj.mdef are different for both tests, since
the private mailboxes test move the mailboxes inside source
code. So, both mdef files will need to be updated at
the same time.
Change-Id: I52ccc5931b1abfd3ae3d654f888d4a019268bba0
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Daniel Leung