Merge pull request #6861 from gebart/pr/cpuid-generic

boards/ek-lm4f120xl/Makefile.features

cpu/cc2538/include/periph_cpu.h

cpu/cc2538/periph/cpuid.c

cpu/cc26x0/include/periph_cpu.h

cpu/cc26x0/periph/cpuid.c

cpu/ezr32wg/include/periph_cpu.h

cpu/ezr32wg/periph/cpuid.c

cpu/kinetis_common/include/periph_cpu.h

cpu/kinetis_common/periph/cpuid.c

cpu/lm4f120/periph/cpuid.c

cpu/nrf5x_common/include/periph_cpu_common.h

cpu/nrf5x_common/periph/cpuid.c

cpu/sam0_common/periph/cpuid.c

cpu/stm32_common/include/periph_cpu_common.h

drivers/periph_common/cpuid.c