habanalabs: use get_task_pid() to take PID

find_get_pid() isn't good in case the user process was run inside
docker.

As a result, we didn't had the PID and we couldn't kill the user
process in case the device got stuck and we needed to reset the
device.

Signed-off-by: Dani Liberman <dliberman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>