dmaengine: hsu: allow more than 3 descriptors

Current code allows only up to 3 descriptors to be programmed to the hardware
since it is used wrong calculations. Change % to min_t() to allow as many
descriptors as user supplied. At once it could be programmed up to 4
descriptors due to hardware limitations.

The issue was found under stress test, so it might not bother ordinary users.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>