hw_breakpoint: Introduce "struct bp_cpuinfo"

This patch simply moves all per-cpu variables into the new
single per-cpu "struct bp_cpuinfo".

To me this looks more logical and clean, but this can also
simplify the further potential changes. In particular, I do not
think this memory should be per-cpu, it is never used "locally".
After this change it is trivial to turn it into, say,
bootmem[nr_cpu_ids].

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155020.GA6350@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>