If nr_cpus < nr_iaa, the calculated cpus_per_iaa will be 0, which
causes a divide-by-0 in rebalance_wq_table().

Make sure cpus_per_iaa is 1 in that case, and also in the nr_iaa == 0
case, even though cpus_per_iaa is never used if nr_iaa == 0, for
paranoia.

Cc: <stable@vger.kernel.org> # v6.8+
Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>