The proposed change will remove usage of the module parameters as global
variables. In future it helps to run different test cases sequentially.

The patch introduces the run_threaded_test() and stop_threaded_test() functions
that could be used later outside of dmatest_init, dmatest_exit scope.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>