crypto: qat - fix heartbeat error injection

crypto: qat - fix heartbeat error injection

The current implementation of the heartbeat error injection uses
adf_disable_arb_thd() to stop a specific accelerator engine thread
from processing requests. This does not reliably prevent the device
from generating responses.

Fix the error injection by disabling the device arbiter through
exit_arb() instead. This properly simulates a device failure by
stopping all arbitration, which results in missing responses for
sent requests.

Remove the now unused adf_disable_arb_thd() function and its
declaration.

Fixes: e2b67859ab6e ("crypto: qat - add heartbeat error simulator")
Signed-off-by: Damian Muszynski <damian.muszynski@intel.com>
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>