Make slow tests on arm64

TBR=bmeurer@chromium.org, ishell@chromium.org

Review URL: https://codereview.chromium.org/701023003

Cr-Commit-Position: refs/heads/master@{#25160}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25160 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/mjsunit.status

@@ -299,6 +299,8 @@
   'array-reduce': [PASS, SLOW],
   'array-sort': [PASS, SLOW],
   'array-splice': [PASS, SLOW],
+  'asm/embenchen/box2d': [PASS, SLOW],
+  'asm/embenchen/lua_binarytrees': [PASS, SLOW],
   'bit-not': [PASS, SLOW],
   'compiler/alloc-number': [PASS, SLOW],
   'compiler/osr-assert': [PASS, SLOW],