cmd/internal/gc, cmd/internal/obj: remove pointless fmt.Sprintf calls

This is a follow-up to CL 6265. No behavior changes.
The diff was generated with eg, using template:

package p

import "fmt"

func before(a string) string { return fmt.Sprintf(a) }
func after(a string) string  { return a }

Change-Id: I7b3bebf31be5cd1ae2233da06cb4502a3d73f092
Reviewed-on: https://go-review.googlesource.com/6269
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/internal/gc/init.go b/src/cmd/internal/gc/init.go
index a7d4fbd..3c27bd6 100644
--- a/src/cmd/internal/gc/init.go
+++ b/src/cmd/internal/gc/init.go
@@ -118,7 +118,7 @@
 	r := (*NodeList)(nil)
 
 	// (1)
-	namebuf = fmt.Sprintf("initdoneĀ·")
+	namebuf = "initdoneĀ·"
 
 	gatevar := newname(Lookup(namebuf))
 	addvar(gatevar, Types[TUINT8], PEXTERN)
@@ -126,7 +126,7 @@
 	// (2)
 	Maxarg = 0
 
-	namebuf = fmt.Sprintf("init")
+	namebuf = "init"
 
 	fn := Nod(ODCLFUNC, nil, nil)
 	initsym := Lookup(namebuf)