runtime: correct netbsd/amd64 assembly for timespec handling
runtime: correct netbsd/amd64 assembly for timespec handling

A timespec on netbsd/amd64 is int64/int64, not int64/int32.
This bug appears to have been introduced in 7777bac6e45.

Spotted by Cherry Zhang while reviewing https://go-review.googlesource.com/c/go/+/177120.

Change-Id: I163c55d926965defd981bdbfd2511de7d9d4c542
Reviewed-on: https://go-review.googlesource.com/c/go/+/177637
Reviewed-by: Benny Siegert <05f4aee36fd25d0de2a07789fd6e73398db492cc@gmail.com>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Benny Siegert <05f4aee36fd25d0de2a07789fd6e73398db492cc@gmail.com>

akutz/go,golang/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,cloudflare/go,nawawi/go,akutz/go,akutz/go,nawawi/go,CAFxX/go,nawawi/go,akutz/go,cloudflare/go,nawawi/go,golang/go,akutz/go,akutz/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,golang/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,golang/go,akutz/go,cloudflare/go,CAFxX/go,akutz/go