Revert of Split rsqrt into rsqrt{0,1,2}, with increasing cost and precision on ARM...

Revert of Split rsqrt into rsqrt{0,1,2}, with increasing cost and precision on ARM (patchset #2 id:20001 of https://codereview.chromium.org/1109913002/)

Reason for revert:
arm64 typos

Original issue's description:
> Split rsqrt into rsqrt{0,1,2}, with increasing cost and precision on ARM
>
> This is a logical no-op.  Everything was using the equivalent of rsqrt1() before, and is now after.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/9de16283fdc8cc0d31a84f503578d0ecea4e8297

TBR=reed@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1105233003