mem: use z specifier to format size_t
mem: use z specifier to format size_t

The recommended way to format size_t in printf is to use the
z modifier which handles the case where size_t maybe 32 or 64 bits.

Signed-off-by: Stephen Hemminger <06fa905d7f2aaced6dc72e9511c71a2a51e8aead@networkplumber.org>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk