cmd/internal/obj: do not generate data for $f32. and $f64. symbols at assemble time

When reading the object files for linking, liblink takes care of
generate the data for them.

This is a port of https://golang.org/cl/3101 to Go.

Change-Id: Ie3e2d6515bd7d253a8c1e25c70ef8fed064436d8
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/8383Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/obj/arm/obj5.go

@@ -112,11 +112,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
-			if s.Type == 0 {
-				s.Type = obj.SRODATA
-				obj.Adduint32(ctxt, s, i32)
-			}
-
 			p.From.Type = obj.TYPE_MEM
 			p.From.Sym = s
 			p.From.Name = obj.NAME_EXTERN
@@ -128,11 +123,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
-			if s.Type == 0 {
-				s.Type = obj.SRODATA
-				obj.Adduint64(ctxt, s, i64)
-			}
-
 			p.From.Type = obj.TYPE_MEM
 			p.From.Sym = s
 			p.From.Name = obj.NAME_EXTERN

src/cmd/internal/obj/x86/obj6.go

@@ -249,11 +249,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 			i32 := math.Float32bits(f32)
 			literal := fmt.Sprintf("$f32.%08x", i32)
 			s := obj.Linklookup(ctxt, literal, 0)
-			if s.Type == 0 {
-				s.Type = obj.SRODATA
-				obj.Adduint32(ctxt, s, i32)
-			}
-
 			p.From.Type = obj.TYPE_MEM
 			p.From.Name = obj.NAME_EXTERN
 			p.From.Sym = s
@@ -293,11 +288,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 			i64 := math.Float64bits(p.From.Val.(float64))
 			literal := fmt.Sprintf("$f64.%016x", i64)
 			s := obj.Linklookup(ctxt, literal, 0)
-			if s.Type == 0 {
-				s.Type = obj.SRODATA
-				obj.Adduint64(ctxt, s, i64)
-			}
-
 			p.From.Type = obj.TYPE_MEM
 			p.From.Name = obj.NAME_EXTERN
 			p.From.Sym = s