papi_internal: fix memory leak
papi_internal: fix memory leak

When I made some changes a while back I forgot to free ESI->NativeBits
properly.

This was causing memory leak warnings on buildbot.

arm-hpc/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi