accel/habanalabs: change the heartbeat scheduling point

accel/habanalabs: change the heartbeat scheduling point

Currently we schedule the heartbeat thread at late init, only then
we set the INTS_REGISTER packet which enables events to be received
from firmware.

Init may take some time and we want to give firmware 2 full cycles of
heartbeat thread after it received INTS_REGISTER.

The patch will move the heartbeat thread scheduling to be after driver
is done with all initializations.

Signed-off-by: Farah Kassabri <fkassabri@habana.ai>
Reviewed-by: Ofir Bitton <obitton@habana.ai>
Signed-off-by: Ofir Bitton <obitton@habana.ai>