perf mem: Move the mem_operations global to struct perf_mem

perf mem: Move the mem_operations global to struct perf_mem

Just like the other parameters, grouping it on the builtin-mem specific
config area: struct perf_mem.

Acked-by: Stephane Eranian <eranian@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Fowles <rfowles@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-ad8ns5l51ongemfsir3zy09x@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>