x86: Adjust board_f.c for x86

For x86, things have adjusted somewhat since this series was originally
written. It has its own way of running through initcalls which is actually
nicer than others archs.

Unfortunately this does introduce exceptions. We will soon require use of
generic board on x86, but until then we need to fit in with what is there,
and treat x86 as a special case.

Signed-off-by: Simon Glass <sjg@chromium.org>