Enable PFFFT_ENABLE_NEON for arm64

NEON is the default for all arm64 devices.

Bug: 159685774
Test: HOST_CROSS_OS=linux_bionic HOST_CROSS_ARCH=arm64 m \
out/soong/host/linux_bionic-arm64/bin/webRTC

Change-Id: I1d71e970e8043e915ad5cc18d3253d467ab20e20
diff --git a/Android.bp b/Android.bp
index 1bd09c0..dad90bb 100644
--- a/Android.bp
+++ b/Android.bp
@@ -2,16 +2,16 @@
     name: "libpffft",
     srcs: [
         "pffft.c",
-	"pffft_common.c",
+        "pffft_common.c",
     ],
     local_include_dirs: ["."],
     export_include_dirs: ["."],
     host_supported: true,
     device_supported: false,
     visibility: ["//external/webrtc:__subpackages__"],
-    target: {
-        linux_bionic_arm64: {
-            cflags: ["-DPFFFT_SIMD_DISABLE"],
+    arch: {
+        arm64: {
+            cflags: ["-DPFFFT_ENABLE_NEON"],
         },
     },
 }