Optimize fixed-point celt_inner_prod() and dual_inner_prod() for ARM NEON

This optimization is bit exact with C functions.

Change-Id: Ia9ce6dd3c20d2f56dbd43ddc02d1a6fd6554608d

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>
4 files changed