doc: mark legacy adc API as deprecated
drivers: mark adc.h as legacy
cpu: use adc_legacy.h where appropriate
cpu/mc1322x: rename adc header to mc1322x-adc
drivers/adc_legacy: add copyright, author
cpu/mc1322x: fix mc1322x-adc.h license
cpu/mc1322x: fix mc1322x-adc.h cpp compatability
Merge pull request #1877 from LudwigOrtmann/adc_legacy

ADC legacy