cpu/sam0_common: update README for SAML1x addition
cpu/sam0_common: update README for SAML1x addition

Rewrite the README to reflect the recent addition of SAMR30 and
SAML10/SAML11.

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