board_f: x86: Use checkcpu() for CPU init

At present we misuse print_cpuinfo() do so CPU init on x86. This is done
because it is the next available call after the console is enabled. But
several arches use checkcpu() instead. Despite the horrible name (which
we can fix), it seems a better choice.

Adjust the various x86 CPU implementations to move their init code into
checkcpu() and use print_cpuinfo() only for printing CPU info.

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