perf/x86/uncore: add ability to customize pmu callbacks

perf/x86/uncore: add ability to customize pmu callbacks

This patch enables custom struct pmu callbacks per uncore
PMU types. This feature may be used to simplify counter
setup for certain uncore PMUs which have free running
counters for instance. It becomes possible to bypass
the event scheduling phase of the configuration.

Cc: mingo@elte.hu
Cc: acme@redhat.com
Cc: ak@linux.intel.com
Cc: zheng.z.yan@intel.com
Cc: peterz@infradead.org
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1392132015-14521-3-git-send-email-eranian@google.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>