meta-iotlab: refactor openocd recipes

[aabadie]

• default version in /usr/local now becomes 0.10
• use git version in /opt/openocd-dev
• remove useless openocd_last recipe

Once this is merged the gateway code will have to be updated as well: some boards are using the openocd_last version so will be broken.

M3/FOX and a few others already uses the new git version so should still work.

[aabadie]

~Don't merge, there are build issues with the git version~ => fixed