cpu/stm32_common/i2c: Fix error handling in i2c_1.c
cpu/stm32_common/i2c: Fix error handling in i2c_1.c

Errors flags could not clear making the i2c unusable after error.
This fix removes the error check in start so the error flags can clear and does proper checking for status bits before _bus_check.

basilfx/RIOT,RIOT-OS/RIOT,mtausig/RIOT,authmillenon/RIOT,jasonatran/RIOT,mfrey/RIOT,lazytech-org/RIOT,OTAkeys/RIOT,mtausig/RIOT,smlng/RIOT,lazytech-org/RIOT,jasonatran/RIOT,authmillenon/RIOT,josephnoir/RIOT,kYc0o/RIOT,toonst/RIOT,kYc0o/RIOT,gebart/RIOT,authmillenon/RIOT,mfrey/RIOT,mtausig/RIOT,authmillenon/RIOT,kaspar030/RIOT,biboc/RIOT,jasonatran/RIOT,basilfx/RIOT,OlegHahm/RIOT,authmillenon/RIOT,miri64/RIOT,toonst/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,mfrey/RIOT,basilfx/RIOT,OlegHahm/RIOT,josephnoir/RIOT,ant9000/RIOT,BytesGalore/RIOT,smlng/RIOT,yogo1212/RIOT,A-Paul/RIOT,mtausig/RIOT,josephnoir/RIOT,toonst/RIOT,aeneby/RIOT,ant9000/RIOT,smlng/RIOT,josephnoir/RIOT,x3ro/RIOT,OlegHahm/RIOT,basilfx/RIOT,rfuentess/RIOT,toonst/RIOT,rfuentess/RIOT,yogo1212/RIOT,cladmi/RIOT,miri64/RIOT,rfuentess/RIOT,rfuentess/RIOT,mtausig/RIOT,OTAkeys/RIOT,miri64/RIOT,x3ro/RIOT,kYc0o/RIOT,smlng/RIOT,BytesGalore/RIOT,jasonatran/RIOT,kaspar030/RIOT,aeneby/RIOT,yogo1212/RIOT,biboc/RIOT,kYc0o/RIOT,miri64/RIOT,authmillenon/RIOT,lazytech-org/RIOT,kaspar030/RIOT,yogo1212/RIOT,OTAkeys/RIOT,x3ro/RIOT,A-Paul/RIOT,lazytech-org/RIOT,BytesGalore/RIOT,gebart/RIOT,kaspar030/RIOT,A-Paul/RIOT,yogo1212/RIOT,rfuentess/RIOT,OlegHahm/RIOT,aeneby/RIOT,ant9000/RIOT,RIOT-OS/RIOT,toonst/RIOT,OTAkeys/RIOT,mfrey/RIOT,miri64/RIOT,A-Paul/RIOT,BytesGalore/RIOT,gebart/RIOT,cladmi/RIOT,A-Paul/RIOT,biboc/RIOT,basilfx/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,gebart/RIOT,cladmi/RIOT,OTAkeys/RIOT,gebart/RIOT,biboc/RIOT,aeneby/RIOT,x3ro/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,jasonatran/RIOT,cladmi/RIOT,x3ro/RIOT,yogo1212/RIOT,smlng/RIOT,lazytech-org/RIOT,biboc/RIOT,ant9000/RIOT,mfrey/RIOT,OlegHahm/RIOT,cladmi/RIOT,aeneby/RIOT,BytesGalore/RIOT,ant9000/RIOT