perf, x86: P4 PMU -- fix typo in unflagged NMI handling

Tested-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
LKML-Reference: <1274174954.22793.17.camel@minggr.sh.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>