Fix arm64 deoptimization from double registers (reverts r20613).

This reverts "ARM64: Use pair memory access in deoptimizer entry", r20613. It does not really make sense to micro-optimize the deoptimizer as it is the ultra-slow path. Moreover, the original code was easier to read (in addition to being correct).

BUG=391313
LOG=N
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/389583003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22360 ce2b1a6d-e550-0410-aec6-3dcde31c8c00