powerpc/oprofile: IBM CELL: add SPU event profiling support

This patch adds the SPU event based profiling funcitonality for the
IBM Cell processor.  Previously, the CELL OProfile kernel code supported
PPU event, PPU cycle profiling and SPU cycle profiling.   The addition of
SPU event profiling allows the users to identify where in their SPU code
various SPU evnets are occuring.  This should help users further identify
issues with their code.  Note, SPU profiling has some limitations due to HW
constraints.  Only one event at a time can be used for profiling and SPU event
profiling must be time sliced across all of the SPUs in a node.

The patch adds a new arch specific file to the OProfile file system. The
file has bit 0 set to indicate that the kernel supports SPU event profiling.
The user tool must check this file/bit to make sure the kernel supports
SPU event profiling before trying to do SPU event profiling.  The user tool
check is part of the user tool patch for SPU event profiling.

Signed-off-by: Carl Love <carll@us.ibm.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>