syscall: add missing TIOCGSID for openbsd/386
syscall: add missing TIOCGSID for openbsd/386

The previous syscall constants regeneration on openbsd was conducted
with OpenBSD current 3 months ago and it missed updating openbsd/386.
This CL adds TIOCGSID for fixing the inconsistency between opensbd/amd64
and openbsd/386.

Update issue 7049

LGTM=iant
R=jsing, rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/96960044

d0f/go-zh,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,webfd/go-zh,webfd/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,d0f/go-zh,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,bryanxu/go-zh,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh