mem: lock pages when not using hugepages

mem: lock pages when not using hugepages

Although the physical address won't be correct in memory segment,
this allows at least to retrieve the physical address using
rte_mem_virt2phy(). Indeed, if the page is not locked, the page
may not be present in physical memory.

With next commit, it allows a mempool to have properly filled physical
addresses when using --no-huge option.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>