x86/perf/intel/cstate: Sanitize probing

The whole probing functionality can simply be expressed with model matching
and a bunch of structures describing the variants. This is a first step to
make that driver modular.

While at it, get rid of completely pointless comments and name the enums so
they are self explaining.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ Reworked probing to clear msr[].attr for all !present msrs. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20160320185623.500381872@linutronix.deSigned-off-by: Ingo Molnar <mingo@kernel.org>