driver: use syscall number from golang.org/x/sys/unix
driver: use syscall number from golang.org/x/sys/unix

Use unix.SYS_SCHED_SETAFFINITY instead of duplicating the syscall number
locally. This also adds support (in principle) for mips, mipsle, ppc64le
and sparc64.

Change-Id: I873c7df4c3d0590fd80e4ecc05410d0023252894
Reviewed-on: https://go-review.googlesource.com/77471
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/benchmarks,golang/benchmarks