app/pdump: call EAL cleanup before exit

This patch adds a call to the newly introduced cleanup()
function just before quitting the pdump app.

Adding this function call before quitting from a secondary processes
is important, as otherwise it will leak hugepage memory. For a secondary
process that is run multiple times, this could cause hugepage memory
to become depleted and stop a secondary process from starting.

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Vipin Varghese <vipin.varghese@intel.com>