By using 0xff for a short it was not setting the high bits. When
comparing the output with vtst to find non-zero elements it was skipping
vaules which had no low bits set such as -512 / 0xFE00.
Using -8191 as the first element of coeff will generate this condition.
BUG=883
Change-Id: Ia1e10fb809d1e7866f28c56769fe703e6231a657
Use intrinsics for neon quantization. Slight loss (<5%) of performance
compared to the assembly. Roughly 10x faster on arm64 because that was
running C code before.
Change-Id: I7cf5242d8f29b7eab5bca6a1c20c89c9fc9ca66d
