perf/x86/intel/uncore: Enable EV_SEL_EXT bit for PCU

This patch adds support for the SNB-EP PCU uncore PMU extra_sel_bit
(bit 21) which is missing from the documentation in Table-2.75 of
Intel Xeon Processor E5-2600 Product Family Uncore Performance
Monitoring Guide. It is referred to later in Table-2.81. Without
this selection bit explicitly enabled by the kernel, some events
such as COREx_TRANSITION_CYCLES do not count correctly.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1376375382-21350-4-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>