Missing tests for xcore AI

[ed-xmos]

Only backpressure test and AN00162 compile and run on xcore AI hardware in Jenkins. The other tests require in depth usage of xmostest and xsim. So even running them on the xcore AI HW target is not really helpful. The best we could do is run these using an xcore AI xsim target, which should be fine. Given these run successfully on xcore 200 target already, the risk to not having these is very low. The missing tests are:

test_basic_frame_master.py test_basic_frame_master_external_clock.py test_basic_frame_slave.py test_basic_master.py test_basic_slave.py test_index_sequence.py test_slave_bclk_invert.py test_slave_index_sequence.py test_tdm_index_sequence.py test_tdm_master_cb.py

In addition, the following following examples are not built under XS3 (or tested to see if they can be downloaded)

app_i2s_frame_loopback_demo app_i2s_frame_slave_loopback_demo app_simple_i2s_frame_master app_simple_i2s_frame_master_external_clock app_simple_i2s_frame_slave app_simple_i2s_master app_simple_i2s_slave app_simple_tdm_master app_tdm_loopback_demo

[ACascarino]

To complete in tandem with #104