accel/habanalabs: move heartbeat work initialization to early init

accel/habanalabs: move heartbeat work initialization to early init

The device heartbeat work is currently initialized at
device_heartbeat_schedule() which is called at the end of
hl_device_init().
However hl_device_init() can fail at a previous step, and in such a
case, a subsequent call to hl_device_fini() will lead to calling
cleanup_resources() and accessing this work uninitialized.

As there is no real need to re-initialize this work every time it is
rescheduled, move this initialization to device_early_init() to be done
once and early enough.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Ofir Bitton <obitton@habana.ai>
Signed-off-by: Ofir Bitton <obitton@habana.ai>