x86: conditionalize code for ARM neon optimization
x86: conditionalize code for ARM neon optimization

Conditionalize code for ARM neon optimizations so that other architectures
compile correctly.

Change-Id: I538b937734f3e6a3b318e40fcc45579bfa899f28

Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia,Fusion-Rom/android_external_skia