This reverts commit 548fda4a.

Reason for revert: Segfault on nosse bot: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux/35905?

Original change's description:
> [liftoff] Check fp_pair when looking up register for reuse
> 
> Given two registers that are both not gp_pair, one could be an fp_pair,
> and the other not, and we will incorrect call == on them. The current
> check needs to be expanded to check that both registers are fp_pair.
> 
> Bug: chromium:1054466
> Change-Id: Ib986c002a8a5cadb9668458597a797cecfd971b1
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2070006
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66402}

TBR=clemensb@chromium.org,zhin@chromium.org

Change-Id: I56f13406ef3cc3793c9d0e2273c4dc5fb0e3de38
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1054466
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2069327Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66405}