test: fix build on GOARCH=ppc64/ppc64le

Change-Id: Ibf2879c0034250c5699e21ecea0eb76340597a2a
Reviewed-on: https://go-review.googlesource.com/10810
Reviewed-by: Austin Clements <austin@google.com>

Author: minux

test/nosplit.go

@@ -249,7 +249,7 @@ TestCases:
 		switch goarch {
 		case "ppc64", "ppc64le":
 			ptrSize = 8
-			fmt.Fprintf(&buf, "#define CALL BL\n#define REGISTER (CTR)\n#define RET RETURN\n")
+			fmt.Fprintf(&buf, "#define CALL BL\n#define REGISTER (CTR)\n")
 		case "arm":
 			fmt.Fprintf(&buf, "#define CALL BL\n#define REGISTER (R0)\n")
 		case "arm64":