ARM Deoptimizer: fix TODO from r13484

This lets the Deoptimizer pointer stay in r0, saving a mov and
simplifying the code a little.

BUG=none
TEST=Tested with test/mjsunit/math-floor-of-div.js, this fails reliably if OSR is broken

Review URL: https://chromiumcodereview.appspot.com/12082046
Patch from Hans Wennborg <hans@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13550 ce2b1a6d-e550-0410-aec6-3dcde31c8c00