Remove 8 NEON rounding opcodes, merging them into the existing float
rounding opcodes, since the instruction used is the same, only the
register format is different, and can be determined at codegen time.

Bug: v8:10930
Change-Id: Ice19c1e2a31f6913c748976fe3a021035a752d88
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2436617Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70241}