bluez5: use lc3plus.h instead of lc3.h + fix initial bitrate

The file name "lc3.h" in the ETSI LC3plus package may conflict with the actual LC3 codec, so try to find a file "lc3plus.h" instead. Also try to find a pkg-config dependency for it first (in which case use lc3.h, assuming it's in different directory). This can be fine tuned, if something starts to package that library.

Also fix initial bitrate used.