seems endless-loop exist in QAT_engine

ENV:
`QAT_engine v0.5.30`
`driver 1.7`
`Nginx + openssl 1.1.2`

Action:
Reload Nginx frequently under high load and then I found a woker process is in endless-loop even there is no any request.

```
#0 0x00007fd84b3ab461 in sigwait () from /lib64/libpthread.so.0
#1 0x00007fd84ab9c3a1 in timer_poll_func (ih=) at qat_polling.c:163
#2 0x00007fd84b3a3e25 in start_thread () from /lib64/libpthread.so.0
#3 0x00007fd84b0cdbad in clone () from /lib64/libc.so.6
Thread 1 (Thread 0x7fd84c07d740 (LWP 75851)):
#0 0x00007fd84b0b2a47 in sched_yield () from /lib64/libc.so.6
#1 0x00007fd84aba49a0 in qat_ecdh_compute_key (outX=outX@entry=0x7fff896d0538, outlenX=outlenX@entry=0x7fff896d0548, outY=outY@entry=0x7fff896d0540, outlenY=outlenY@entry=0x7fff896d0550, pub_key=, ecdh=ecdh@entry=0x294f2a0) at qat_ec.c:537
#2 0x00007fd84aba4c66 in qat_ecdh_generate_key (ecdh=0x294f2a0) at qat_ec.c:713
#3 0x0000000000662a3f in EVP_PKEY_keygen (ctx=ctx@entry=0x294fa70, ppkey=ppkey@entry=0x7fff896d05c0) at crypto/evp/pmeth_gn.c:108
#4 0x000000000051097f in ssl_generate_pkey_group (s=s@entry=0x25cb810, id=id@entry=23) at ssl/s3_lib.c:5232
#5 0x000000000055372d in tls_construct_server_key_exchange (s=0x25cb810, pkt=0x7fff896d07d0) at ssl/statem/statem_srvr.c:2935
#6 0x00000000005456ea in write_state_machine (s=0x25cb810) at ssl/statem/statem.c:980
#7 state_machine (s=0x25cb810, server=1) at ssl/statem/statem.c:456
#8 0x000000000051e307 in SSL_do_handshake (s=0x25cb810) at ssl/ssl_lib.c:3657
#9 0x000000000048e900 in ngx_ssl_handshake (c=c@entry=0x7fd840e7d550) at src/event/ngx_event_openssl.c:1382
.....
```
```
$sudo cat /sys/kernel/debug/qat_dh895xcc_07:00.0/fw_counters
+------------------------------------------------+
| FW Statistics for Qat Device |
+------------------------------------------------+
| Firmware Requests [AE 0]: 2420695 |
| Firmware Responses[AE 0]: 2420695 |
+------------------------------------------------+
| Firmware Requests [AE 1]: 3533795 |
| Firmware Responses[AE 1]: 3533795 |
+------------------------------------------------+
| Firmware Requests [AE 2]: 2421889 |
| Firmware Responses[AE 2]: 2421889 |
+------------------------------------------------+
| Firmware Requests [AE 3]: 3533834 |
| Firmware Responses[AE 3]: 3533834 |
+------------------------------------------------+
| Firmware Requests [AE 4]: 2422055 |
| Firmware Responses[AE 4]: 2422055 |
+------------------------------------------------+
| Firmware Requests [AE 5]: 3533431 |
| Firmware Responses[AE 5]: 3533431 |
+------------------------------------------------+
| Firmware Requests [AE 6]: 2420962 |
| Firmware Responses[AE 6]: 2420962 |
+------------------------------------------------+
| Firmware Requests [AE 7]: 3532819 |
| Firmware Responses[AE 7]: 3532819 |
+------------------------------------------------+
| Firmware Requests [AE 8]: 2420851 |
| Firmware Responses[AE 8]: 2420851 |
+------------------------------------------------+
| Firmware Requests [AE 9]: 3532721 |
| Firmware Responses[AE 9]: 3532721 |
+------------------------------------------------+
| Firmware Requests [AE 10]: 2420981 |
| Firmware Responses[AE 10]: 2420981 |
+------------------------------------------------+
| Firmware Requests [AE 11]: 3533445 |
| Firmware Responses[AE 11]: 3533445 |
+------------------------------------------------+
```
Seem that the driver works correctly, any suggestions ?