perf/x86/cstate: Remove unused 'struct perf_cstate_msr'

Use of this structure was removed in:

  8f2a28c5 ("perf/x86/cstate: Use new probe function")

Remove the now stale type as well.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/events/intel/cstate.c

@@ -143,12 +143,6 @@ struct cstate_model {
 #define SLM_PKG_C6_USE_C7_MSR	(1UL << 0)
 #define KNL_CORE_C6_MSR		(1UL << 1)
 
-struct perf_cstate_msr {
-	u64	msr;
-	struct	perf_pmu_events_attr *attr;
-};
-
-
 /* cstate_core PMU */
 static struct pmu cstate_core_pmu;
 static bool has_cstate_core;