Before the offending commit, mlx5 core did the IRQ affinity itself,
and it seems that the new generic code have some drawbacks and one
of them is the lack for user ability to modify irq affinity after
the initial affinity values got assigned.
The issue is still being discussed and a solution in the new generic code
is required, until then we need to revert this patch.
This fixes the following issue:
echo <new affinity> > /proc/irq/<x>/smp_affinity
fails with -EIO
This reverts commit a435393acafbf0ecff4deb3e3cb554b34f0d0664.
Note: kept mlx5_get_vector_affinity in include/linux/mlx5/driver.h since
> it is used in mlx5_ib driver.
This won't work for sure because the msi_desc affinity cpumask won't
ever be populated. You need to re-implement it in mlx5 if you don't want
to break rdma ULPs that rely on it.
