unix: fix cpuset size argument in sched_affinity syscall
unix: fix cpuset size argument in sched_affinity syscall

Fixes golang/go#23639

Change-Id: I7793dc50de35791a7c8af1966bb2ee4a36a2ac1c
Reviewed-on: https://go-review.googlesource.com/91375
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

multiplay/golang-sys,golang/sys,multiplay/golang-sys,golang/sys,golang/sys,multiplay/golang-sys,multiplay/golang-sys