board_f: m68k: Factor out m68k-specific bdinfo setup

Factor out m68k-specific bdinfo setup to arch_setup_bdinfo in
arch/m68k/lib/bdinfo.c. Also, use if(IS_ENABLED()) instead of #ifdef where
possible.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>