Revert of Disable NEON procs for box blur as it produces invalid results (patchset #1 id:1 of https://codereview.chromium.org/520963002/)

Reason for revert:
failing more GMs than expected.

Original issue's description:
> Disable NEON procs for box blur as it produces invalid results
>
> BUG=skia:2845
>
> Committed: https://skia.googlesource.com/skia/+/4a1764688c990fb926aaeab538497dad52768d99

R=senorblanco@google.com, mtklein@google.com
TBR=mtklein@google.com, senorblanco@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2845

Author: djsollen@google.com

Review URL: https://codereview.chromium.org/531023002
2 files changed