J. David Ibáñez c965ce3de6 boards/common/arduino-atmega: define F_CPU
This fixes the following error:

$ BOARD=arduino-mega2560 make -C tests/pkg_arduino_sdi_12/
[...]
[...]/RIOT/build/pkg/arduino_sdi_12/src/SDI12_boards.cpp:35:16: error: ‘preSDI12_TCCR2B’ defined but not used [-Werror=unused-variable
   35 | static uint8_t preSDI12_TCCR2B;
2021-10-28 15:59:40 +02:00
..