Cell OProfile: Incorrect local array size in activate spu profiling function

Updated the patch to address comments by Michael Ellerman.
Specifically, changed upper limit in for loop to
ARRAY_SIZE() macro and added a check to make sure the
number of events specified by the user, which is used as
the max for indexing various arrays, is no bigger then the
declared size of the arrays.

The size of the pm_signal_local array should be equal to the
number of SPUs being configured in the array.  Currently, the
array is of size 4 (NR_PHYS_CTRS) but being indexed by a for
loop from 0 to 7 (NUM_SPUS_PER_NODE).

Signed-off-by: Carl Love <carll@us.ibm.com>