habanalabs: flush EQ workers in hard reset

During hard-reset, there can be multiple events received from the H/W. For
each event, the driver opens a worker thread to handle it. For some of the
events, the driver will read/write registers in the code that handles the
event.

In case of hard-reset, we must prevent reads/writes to the registers during
the reset operation because the device might get stuck if that happens.

Therefore, flush the EQ workers before resetting the device (in hard-reset
only). Additional events won't arrive as we synced and disabled the
interrupts.

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