x86: introduce struct cpa_data

The number of arguments which need to be transported is increasing
and we want to add flush optimizations and large page preserving.

Create struct cpa data and pass a pointer instead of increasing the
number of arguments further.

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