perf, powerpc: Fix up flush_branch_stack() users

The recent LBR rework for x86 left a stray flush_branch_stack() user in
the PowerPC code, fix that up.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/perf_event.h

@@ -261,11 +261,6 @@ struct pmu {
 	 */
 	int (*event_idx)		(struct perf_event *event); /*optional */
 
-	/*
-	 * flush branch stack on context-switches (needed in cpu-wide mode)
-	 */
-	void (*flush_branch_stack)	(void);
-
 	/*
 	 * context-switches callback
 	 */