hifive1: Add RENODE_UART variable to board.cmake

Set RENODE_UART variable describing which UART device
should be used when running Robot Framework test on the platform.

Signed-off-by: Michał Szprejda <mszprejda@antmicro.com>
Signed-off-by: Mateusz Hołenko <mholenko@antmicro.com>
1 file changed