perf/x86: add Intel SkyLake uncore IMC PMU support

perf/x86: add Intel SkyLake uncore IMC PMU support

This patch enables the uncore_imc PMU for Intel
SkyLake Desktop processors (Core i7-6700, model 94).

It is possible to compute memory read/write bandwidth
using:

  $ perf stat -a -e uncore_imc/data_reads/,uncore_imc/data_writes/ ....

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: kan.liang@intel.com
Link: http://lkml.kernel.org/r/1452151546-8853-1-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>