All STM32 family pwr.h must use LIBOPENCM3_PWR_H as include guard so that pwr_common.h can detect that it has been referenced by pwr.h for each family. F2 and F3 had the wrong include guard. Fixes Github issue #513
All STM32 family pwr.h must use LIBOPENCM3_PWR_H as include guard so that pwr_common.h can detect that it has been referenced by pwr.h for each family. F2 and F3 had the wrong include guard. Fixes Github issue #513