perf_counter vs. oprofile

Paul, I just noticed that right now if perf counter is enabled, the
oprofile module load will always fail because the powerpc perf counter
support unconditionally grabs the PMC hardware using
reserve_pmc_hardware() in an arch_initcall()

There really needs to be a way to segregate these multiple users of
the PMC device.  For example, if I'm not using the perf counter
APIs at all I should be able to use oprofile if I want to.

Anyways, just FYI...