misc/nacl: add cmd/vendor/golang.org/x/arch/arm64/arm64asm testdata

This should fix NaCl build failure for CL 49530.

Change-Id: Id9a54f0c81b1b5db5b5efb12a2ad6509c4ab42b3
Reviewed-on: https://go-review.googlesource.com/55770Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

misc/nacl/testzip.proto

@@ -64,6 +64,10 @@ go	src=..
 								armasm
 									testdata
 										+
+							arm64
+								arm64asm
+									testdata
+										+
 							x86
 								x86asm
 									testdata