perf pmu-events: Add Skylake frontend MSR support

Add support for the "frontend" extra MSR on Skylake in the JSON
conversion.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1473978296-20712-19-git-send-email-sukadev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/jevents.c

@@ -127,6 +127,7 @@ static struct msrmap {
 	{ "0x3F6", "ldlat=" },
 	{ "0x1A6", "offcore_rsp=" },
 	{ "0x1A7", "offcore_rsp=" },
+	{ "0x3F7", "frontend=" },
 	{ NULL, NULL }
 };