runtime: fix RuntimeGogoBytes on windows/amd64

Before 3c0fee10, runtime.gogo was just long enough to align to 64 bytes
on OSs with short get_tls implementations and 80 bytes on OSs with
longer get_tls implementations (Windows, Solaris, and Plan 9).
3c0fee10 added a few instructions, which pushed it to 80 on most OSs,
including Windows and Plan 9, and 96 on Solaris.

Fixes #9770.

Change-Id: Ie84810657c14ab16dce9f0e0a932955251b0bf33
Reviewed-on: https://go-review.googlesource.com/3850Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/runtime/arch1_amd64.go

@@ -8,7 +8,7 @@ const (
 	thechar           = '6'
 	_BigEndian        = 0
 	_CacheLineSize    = 64
-	_RuntimeGogoBytes = 80 + (goos_plan9|goos_solaris|goos_windows)*16
+	_RuntimeGogoBytes = 80 + (goos_solaris)*16
 	_PhysPageSize     = 4096
 	_PCQuantum        = 1
 	_Int64Align       = 8