x86: janitor CPA statistics patch

1) Remove __meminit from update_pages_count. It is used inside
split_pages()

2) Make the code depend on PROC_FS. Doing statistics for nothing is
useless and not adding useless code is nice to the Linux tiny folks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>