[dpdk-stable] Port of mlx5 can not start after setting link-down on dpdk-stable v17.11.2

[Zijie Pan]

Hi commit authors (and maintainers),

Please help to backport patches to fix following issue. 
Here are the steps of testpmd on dpdk-17.11.2:
testpmd> show port info 0

********************* Infos for port 0  *********************
MAC address: E4:1D:2D:E7:0C:FA
Driver name: net_mlx5
Connect to socket: 0
...

testpmd> set link-down port 0
testpmd> 
Port 0: LSC event

testpmd> port stop 0
Stopping ports...
Checking link statuses...
Done
testpmd> port start 0
PMD: net_mlx5: Forcing port 0 link to be up
Fail to start port 0
Please stop the ports first
Done
<== Fail to start the port.

Test is OK if using master of dpdk:
testpmd> set link-down port 0
testpmd> 
Port 0: LSC event

testpmd> port stop 0
Stopping ports...
Checking link statuses...
Done
testpmd> port start 0
Port 0: E4:1D:2D:E7:0C:FA
Checking link statuses...
Done
<== Port can start successfully.

This issue was introduced by following commits:
322e1ce net/mlx5: fix link state on device start
f1e3e97 net/mlx5: fix handling link status event

This issue was fixed with following commit from dpdk (master):
7ba5320 net/mlx5: fix link status behavior

The related patches should be ported into dpdk-stable v17.11.2.

Thanks,
Zijie