Full enable new round implementation on x86/x86_64

Rationale:
Running JIT on Fugu does not always provide a constant area.
In such cases, we need to construct FP constants through stack.
This only applies to x86.

Test: 580-checker-round

BUG=26327751

Change-Id: I7e2c80dafbafbe647cfe9ecb039920bb534c666a