Skeleton dmadevice driver, on the lines of rawdev skeleton, is for
showcasing of the dmadev library.

Design of skeleton involves a virtual device which is plugged into VDEV
bus on initialization.

Also, enable compilation of dmadev skeleton drivers.

Signed-off-by: Chengwen Feng <redacted>
---

<snip>

+/* Count of instances */
+static uint16_t skeldma_init_once;

Either the comment for this line or the variable name need to change as 
they do not line up.

I would suggest:

/* Count of instances, currently only 1 is supported. */

static uint16_t skeldma_count;


Reviewed-by: Conor Walsh <redacted>