mem: prevent preallocated pages from being freed

mem: prevent preallocated pages from being freed

It is common sense to expect for DPDK process to not deallocate any
pages that were preallocated by "-m" or "--socket-mem" flags - yet,
currently, DPDK memory subsystem will do exactly that once it finds
that the pages are unused.

Fix this by marking pages as unfreebale, and preventing malloc from
ever trying to free them.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
Tested-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Tested-by: Gowrishankar Muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>