tools: fix shebang in openocd.sh
tools: fix shebang in openocd.sh

Change shebang in script from `/bin/bash` to `/usr/bin/env bash`,
which fixed problems when `bash` is not available in standard location,
e.g., on non-Linux OSes such as FreeBSD.

toonst/RIOT,aeneby/RIOT,smlng/RIOT,ant9000/RIOT,x3ro/RIOT,smlng/RIOT,OlegHahm/RIOT,aeneby/RIOT,smlng/RIOT,kaspar030/RIOT,kYc0o/RIOT,authmillenon/RIOT,kYc0o/RIOT,rfuentess/RIOT,jasonatran/RIOT,kYc0o/RIOT,authmillenon/RIOT,jasonatran/RIOT,miri64/RIOT,yogo1212/RIOT,kaspar030/RIOT,OTAkeys/RIOT,basilfx/RIOT,mtausig/RIOT,josephnoir/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,rfuentess/RIOT,miri64/RIOT,OlegHahm/RIOT,authmillenon/RIOT,aeneby/RIOT,RIOT-OS/RIOT,smlng/RIOT,ant9000/RIOT,ant9000/RIOT,jasonatran/RIOT,x3ro/RIOT,basilfx/RIOT,basilfx/RIOT,ant9000/RIOT,toonst/RIOT,authmillenon/RIOT,yogo1212/RIOT,OTAkeys/RIOT,toonst/RIOT,mtausig/RIOT,jasonatran/RIOT,smlng/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,yogo1212/RIOT,kYc0o/RIOT,x3ro/RIOT,RIOT-OS/RIOT,aeneby/RIOT,josephnoir/RIOT,ant9000/RIOT,mtausig/RIOT,authmillenon/RIOT,mtausig/RIOT,OlegHahm/RIOT,basilfx/RIOT,rfuentess/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,toonst/RIOT,OlegHahm/RIOT,rfuentess/RIOT,yogo1212/RIOT,mtausig/RIOT,jasonatran/RIOT,kaspar030/RIOT,basilfx/RIOT,x3ro/RIOT,josephnoir/RIOT,miri64/RIOT,josephnoir/RIOT,kYc0o/RIOT,toonst/RIOT,josephnoir/RIOT,kaspar030/RIOT,x3ro/RIOT,aeneby/RIOT,miri64/RIOT,yogo1212/RIOT,OTAkeys/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,miri64/RIOT,yogo1212/RIOT