test_fifo: Reorganize directories

Splits the test into two clear sub-categories: microkernel and nanokernel.
This is done to maintain consistency with other tests that do the same
(e.g. test_obj_tracing, test_sema, test_stackprot, test_timer).

Change-Id: Iddb1ec8d569a9d953fb8af5ce08e87b51995f821
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>
19 files changed