{net, IB}/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.

Fixes: 89d44f0a

("net/mlx5_core: Add pci error handlers to mlx5_core driver")
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>