boards/stm32: introduce shared i2c configuration
boards/stm32: introduce shared i2c configuration

This configuration corresponds to I2C1 connected to PB6 (SCL) and PB7 (SDA)

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