dmaengine: dmatest: Describe members of struct dmatest_info

Kernel documentation validator complains that not all members of
struct dmatest_info are being described. Describe them all.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200424161147.16895-6-andriy.shevchenko@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/dmatest.c

@@ -125,7 +125,10 @@ struct dmatest_params {
 /**
  * struct dmatest_info - test information.
  * @params:		test parameters
+ * @channels:		channels under test
+ * @nr_channels:	number of channels under test
  * @lock:		access protection to the fields of this structure
+ * @did_init:		module has been initialized completely
  */
 static struct dmatest_info {
 	/* Test parameters */