cyclic: Integrate cyclic functionality at bootup in board_r/f

This patch adds a call to cyclic_init() to board_f/r.c, enabling the
common cyclic infrastructure. After this it's possible to add cyclic
functions via cyclic_register().

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>