Merge pull request #7929 from basilfx/feature/thunderboard_v2

boards/sltb001a/Makefile

boards/sltb001a/Makefile.dep

boards/sltb001a/Makefile.features

boards/sltb001a/Makefile.include

boards/sltb001a/board.c

boards/sltb001a/include/board.h

boards/sltb001a/include/gpio_params.h

boards/sltb001a/include/periph_conf.h

cpu/efm32_common/Makefile

cpu/efm32_common/Makefile.dep

cpu/efm32_common/Makefile.features

cpu/efm32_common/Makefile.include

cpu/efm32_common/cpu.c

cpu/efm32_common/doc.txt

cpu/efm32_common/include/periph_cpu.h

cpu/efm32_common/periph/Makefile

cpu/efm32_common/periph/adc.c

cpu/efm32_common/periph/cpuid.c

cpu/efm32_common/periph/dac.c

cpu/efm32_common/periph/flashpage.c