powerpc/perf: Fix sampling enable for PPC970

powerpc/perf: Fix sampling enable for PPC970

commit 9f5f9ffe50e90ed73040d2100db8bfc341cee352 upstream.

The logic to distinguish marked instruction events from ordinary events
on PPC970 and derivatives was flawed.  The result is that instruction
sampling didn't get enabled in the PMU for some marked instruction
events, so they would never trigger.  This fixes it by adding the
appropriate break statements in the switch statement.

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>