tests/posix_semaphore: increase timeout margin
tests/posix_semaphore: increase timeout margin

Otherwise it may break on nrf51 boards where the timeout can be slightly above 100. Using 105us margin seems enough

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