mempool: avoid division by zero

In function call rte_mempool_xmem_size, division by expression total_size
which may be zero has undefined behavior.

Coverity issue: 13243
Fixes: 148f963fb532 ("xen: core library changes")

Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>

lib/librte_mempool/rte_mempool.c

@@ -239,6 +239,9 @@ rte_mempool_xmem_size(uint32_t elt_num, size_t total_elt_sz, uint32_t pg_shift)
 {
 	size_t obj_per_page, pg_num, pg_sz;
 
+	if (total_elt_sz == 0)
+		return 0;
+
 	if (pg_shift == 0)
 		return total_elt_sz * elt_num;