dma: add system calls for dma_start/dma_stop

As per current policy of requiring supervisor mode to register
callbacks, dma_config() is omitted.

A note added about checking the channel ID for start/stop, current
implementations already do this but best make it explicitly
documented.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/scripts/gen_kobject_list.py b/scripts/gen_kobject_list.py
index 2fed49d..50b1ce5 100755
--- a/scripts/gen_kobject_list.py
+++ b/scripts/gen_kobject_list.py
@@ -29,6 +29,7 @@
     "aio_cmp_driver_api",
     "counter_driver_api",
     "crypto_driver_api",
+    "dma_driver_api",
     "flash_driver_api",
     "gpio_driver_api",
     "i2c_driver_api",