Move info about ARMv6-M support to beginning of CHANGELOG.md
Move info about ARMv6-M support to beginning of CHANGELOG.md

This way the first group in "Added" section is about new architectures,
second about new chips and third about new boards.
CezaryGapinski/distortos,jasmin-j/distortos,CezaryGapinski/distortos,jasmin-j/distortos,jasmin-j/distortos,DISTORTEC/distortos,DISTORTEC/distortos,jasmin-j/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,jasmin-j/distortos,DISTORTEC/distortos