[POWERPC] OProfile: fix cbe pm signal routing problem

Fix debug_bus_control and group_control PMU register values set up in
set_pm_event().  Initialize variables before calling set_pm_event().
Delete unused static array and code that initialized it.
Rename constant to better reflect usage.

Signed-off-by: Bob Nelson <rrnelson@us.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>