x86_pmu.enable() is called from x86_pmu_enable() with
cpuc->enabled set to 0.  This means we weren't re-enabling the
counters after a context switch.

This patch just removes the check, as it should't be necessary
(and the equivelent x86_ generic code does not have the checks).

The origin of this problem is the KNC driver being based on the
P6 one.   The P6 driver also has this issue, but works anyway
due to various lucky accidents.
Signed-off-by: NVince Weaver <vincent.weaver@maine.edu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: eranian@gmail.com
Cc: Meadows
Cc: Lawrence F <lawrence.f.meadows@intel.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1210171303290.23243@vincent-weaver-1.um.maine.eduSigned-off-by: NIngo Molnar <mingo@kernel.org>