perf tools: Refactor unit and scale function parameters

Passing pointers to alias modifiers 'unit' and 'scale' isn't very
future-proof since if we add more modifiers to the list we'll end up
passing more arguments.

Instead wrap everything up in a struct perf_pmu_info, which can easily
be expanded when additional alias modifiers are necessary in the future.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1411567455-31264-3-git-send-email-matt@console-pimps.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>