cmd/compile/internal/gc: remove all uses of oconv(op, FmtSharp)

Updates #15462

Replace all use of oconv(op, FmtSharp) with fmt.Printf("%#v", op).
This removes all the callers of oconv.

Change-Id: Ic3bf22495147f8497c8bada01d681428e2405b0e
Reviewed-on: https://go-review.googlesource.com/22530
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 6ec0645..3ba4ba4 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -2285,7 +2285,7 @@
 
 		switch l.Op {
 		default:
-			Fatalf("reorder3 unexpected lvalue %v", oconv(l.Op, FmtSharp))
+			Fatalf("reorder3 unexpected lvalue %#v", l.Op)
 
 		case ONAME:
 			break