perf tools: Remove export.h from MANIFEST

We don't carry an export.h wrapper anymore, remove it from the MANIFEST
file to avoid breaking the make perf-tar targets.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20150826080750.GD22670@krava.redhat.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>