opus: Update to version 1.6.1

opus: Update to version 1.6.1

- Update from version 1.5.2 to 1.6.1
- Update of rootfile
- Changelog
    1.6.1
	fixes several minor issues that were discovered since the 1.6 release.
    1.6.0
	Opus 1.6 builds on the new ML-based features introduced in Opus 1.5.
	Major changes since 1.5 include:
		- A new wideband-to-fullband bandwidth extension (BWE) module
		- Support for 96 kHz audio with Opus HD
		- Significant improvement to Deep Redundancy (DRED)
		- A new 24-bit encoder/decoder API

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>