habanalabs: Add debugfs node for engines status

Command submissions sent to the device are composed of command buffers
which are targeted to different device engines, like DMA and compute
entities. When a command submission gets stuck, knowing in which engine
the stuck is, is crucial for debugging.
This patch adds a debugfs node that exports this information, by
displaying the engines' various registers that assemble their idle/busy
status.
The information retrieval is based on the is_device_idle ASIC function.
The printout in this function, of the first detected busy engine, is
removed because it becomes redundant in the presence of the more
elaborated info of the new debugfs node.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>