perf, powerpc: Fix build borkage

perf, powerpc: Fix build borkage

The patch a8b0ca17b80e ("perf: Remove the nmi parameter from the swevent
and overflow interface") missed a spot in the ppc hw_breakpoint code,
fix this up so things compile again.

Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-09pfip95g88s70iwkxu6nnbt@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>