Currently on X87 platform we use only Double register (stack register) for Turbofan...

Currently on X87 platform we use only Double register (stack register) for Turbofan. So we directly
use 1 as allocatable Double register number when setting up the default register configuration..

It does not change the double register configuration of other platforms.

BUG=v8:4135
LOG=N

Review URL: https://codereview.chromium.org/1164813007

Cr-Commit-Position: refs/heads/master@{#29005}