runtime: fix REFLECTMETHOD macro

Removes spurious equals sign from REFLECTMETHOD macro.

Fixes #29487

Change-Id: Iaa3d85ff57087aa79a259f28816f8b0a552536f3
Reviewed-on: https://go-review.googlesource.com/c/155927
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/textflag.h

@@ -31,4 +31,4 @@
 // TODO(mwhudson): only implemented for ppc64x at present.
 #define NOFRAME 512
 // Function can call reflect.Type.Method or reflect.Type.MethodByName.
-#define REFLECTMETHOD = 1024
+#define REFLECTMETHOD 1024