x86: Move timer_init() call a bit earlier

Currently timer_init() is called in board_r.c which is quite late.
Some vgabios execution requires we set up the i8254 timer correctly,
but video initialization comes before timer_init(). Move the call
to board_f.c.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>