Use R0/R1 instead of R4/R5 for eh_return on ARM

This should unblock removal of  _Unwind_PNaClSetResult{0,1} entirely.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4171
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1151383009
1 file changed