Implement ECU (Error Concealment Unit) block for FR

In I06a21f60db01bfe1c2b838f93866fad1d53fdcd1 the Error Concealment
Unit API for FR codec was introduced. This change implements a
corresponding block.

Note: at the moment, only Full Rate is supported by the ECU API.

Change-Id: Ia929ee04f6be3d842c6ef7bc40cce0fdab16e90a
10 files changed