speex: disable neon for arm64
speex: disable neon for arm64

The neon instructions in libspeex/resample_neon.h fail to compile
on arm64:
Error: unknown mnemonic `vld1.16' -- `vld1.16 {d16},[x3]!'
Error: unknown mnemonic `vld1.16' -- `vld1.16 {d20},[x6]!'
Error: unknown mnemonic `vmull.s16' -- `vmull.s16 q0,d16,d20'
Error: unknown mnemonic `vld1.16' -- `vld1.16 {d16,d17,d18,d19},[x3]!'
Error: unknown mnemonic `vld1.16' -- `vld1.16 {d20,d21,d22,d23},[x6]!'
...

Disable neon on arm64 for now.

Change-Id: Ifa2a99696241f53b2d6b25c2cb4330b819699a6f

MWisBest/android_external_speex,jgcaaprom/android_external_speex,MarshedOut/android_external_speex,geekboxzone/mmallow_external_speex,geekboxzone/lollipop_external_speex,android-ia/platform_external_speex,xin3liang/platform_external_speex,jgcaaprom/android_external_speex,Omegaphora/external_speex,laperry1/android_external_speex,byterom/android_external_speex,CyanogenMod/android_external_speex,geekboxzone/lollipop_external_speex,android-ia/platform_external_speex,TeamExodus/external_speex,MWisBest/android_external_speex,xin3liang/platform_external_speex,DirtyUnicorns/android_external_speex,byterom/android_external_speex,TeamExodus/external_speex,laperry1/android_external_speex,DirtyUnicorns/android_external_speex,CyanogenMod/android_external_speex,Omegaphora/external_speex,MarshedOut/android_external_speex,geekboxzone/mmallow_external_speex