runtime: fix openbsd build notetsleep: nosplit stack overflow         120	assumed on entry to notetsleep         96	after notetsleep uses 24         88	on entry to runtime.semasleep         32	after runtime.semasleep uses 56         24	on entry to runtime.nanotime         -8	after runtime.nanotime uses 32
runtime: fix openbsd build
notetsleep: nosplit stack overflow
        120	assumed on entry to notetsleep
        96	after notetsleep uses 24
        88	on entry to runtime.semasleep
        32	after runtime.semasleep uses 56
        24	on entry to runtime.nanotime
        -8	after runtime.nanotime uses 32

Nanotime seems to be using only 24 bytes of stack space.
Unless I am missing something.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/12041044

bryanxu/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,mhennings/marcohennings-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,mhennings/marcohennings-go,d0f/go-zh,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,webfd/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,webfd/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,mhennings/marcohennings-go,d0f/go-zh