board_f: x86: Rename x86_fsp_init() to arch_fsp_init()

board_f: x86: Rename x86_fsp_init() to arch_fsp_init()

While x86 is the only user and this could in principle be moved to
arch_cpu_init() there is some justification for this being a separate
call. It provides a way to handle init which is not CPU-specific, but
must happen before the CPU can be set up.

Rename the function to be more generic.

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