Implemented fp binops for both 32-bit and 64-bit operands.

Bug: v8:6600
Change-Id: Ide223ad0df58f625adef2b2232d0e93c7dcb3524
Reviewed-on: https://chromium-review.googlesource.com/926802
Commit-Queue: Sreten Kovacevic <sreten.kovacevic@mips.com>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51418}