New unit tests added
------------------------
**Local:** Local test uses the GPIO matrix to connect the master and the
slave on the same board. When the master needs the iomux, the master
uses the GPIOs of its own, the slave connect to the pins by GPIO matrix;
When the slave needs the iomux, the slave uses the GPIOs of its own, the
master connects to the pins by GPIO matrix.
- Provide a new unit test which performs freq scanning in mode 0. It
scans frequency of 1M, 8M, 9M and all frequency steps up to the maximum
frequency allowed.
**M & S**: Master & slave tests performs the test with two boards. The
master and slave use iomux or gpio matrix according to the config.
- Provide a new unit test which performs freq scanning in mode 0. It
scans frequency of 1M, 8M, 9M and all frequency steps up to the maximum
frequency allowed.
- Provide a new unit test which performs mode test with significant
frequencies. It tests mode 0,1,2,3 with low frequency, and the maximum
frequency allowed.
