MFC r341554:
mlx5: Raise fatal IB event when sys error occurs

All other mlx5_events report the port number as 1 based, which is how FW
reports it in the port event EQE. Reporting 0 for this event causes
mlx5_ib to not raise a fatal event notification to registered clients
due to a seemingly invalid port.

All switch cases in mlx5_ib_event that go through the port check are
supposed to set the port now, so just do it once at variable
declaration.

Linux commit:
aba462134634b502d720e15b23154f21cfa277e5

Sponsored by: Mellanox Technologies