Turn on neon instrinsics for arm64 by turning off runtime detection.

+ Also turn off runtime detection for arm32 when we know
the build supports neon.

(cherry picked from commit 7f21a7f1c312334ba3548100d6fbdb5679127026)

Change-Id: Ia1926107bd8e87ebc0ef653ed671808cf9b7451f
Merge "Turn on neon instrinsics for arm64 by turning off runtime detection."