linux pmda: fix cgroup hierarchy metric qa fail on ppc64

Resolve a integer sizing issue causing incorrect values and
resultant failure in qa/443 for big endian 64bit platforms.
libpcp: fix 64bit endian issue in highres event timer code

Red Hat QE folks reported test qa/443 failing for big endian
64 bit platforms.  Turned out to be an incorrect 32-vs-64 bit
endian conversion issue in libpcp, where a 32 bit conversion
routine was incorrectly being used.