audio-convert: Fix endianness conversion function init

Endianness conversion should be based on the sample width instead of the
sample depth.

Fixes #510
3 jobs for audioconvert_fix_endianness_conversion in 5 minutes and 22 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #53896
manifest

00:00:20

 
  Build
passed #53897
build fedora x86_64

00:02:21

 
  Full Builds
passed #53898
build android arm64 api28

00:02:40