cmd/gc: resolve static addresses of the form &x.f at link time

When we do y = &x for global variables x and y, y gets initialized
at link time.  Do the same for y = &x.f if x is a struct and y=&x[5]
if x is an array.

fixes #9217
fixes #9355

Change-Id: Iea3c0ce2ce1b309e2b760e345608fd95460b5713
Reviewed-on: https://go-review.googlesource.com/1691
Reviewed-by: Minux Ma <minux@golang.org>

test/fixedbugs/issue9355.dir/a.go

@@ -0,0 +1,16 @@
+package main
+
+var x struct {
+	a, b, c int64
+	d       struct{ p, q, r int32 }
+	e       [8]byte
+	f       [4]struct{ p, q, r int32 }
+}
+
+var y = &x.b
+var z = &x.d.q
+
+var b [10]byte
+var c = &b[5]
+
+var w = &x.f[3].r