mem: fix possible integer overflow
mem: fix possible integer overflow

It is possible to get an integer overflow if we try to reserve a memzone
with len = 0 (meaning the maximum contiguous space available) and the
maximum available elem size is less than (MALLOC_ELEM_OVERHEAD + align).

Coverity issue: 107111

Fixes: fafcc11985a2 ("mem: rework memzone to be allocated by malloc")

Signed-off-by: Sergio Gonzalez Monroy <efb28dd1236fe58fb57f933212eddfe89b9da704@intel.com>

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