xen: fix build as shared library

When building as shared library, the compiler complains for
	undefined reference to `rte_xen_mem_phy2mch'

The symbol rte_xen_mem_phy2mch was introduced in DPDK 2.2
and has been called in mempool recently via rte_mem_phy2mch.

Fixes: c042ba20674a ("mempool: rework support of Xen dom0")

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>

lib/librte_eal/linuxapp/eal/rte_eal_version.map

@@ -138,6 +138,7 @@ DPDK_2.2 {
 	rte_keepalive_mark_alive;
 	rte_keepalive_register_core;
 	rte_xen_dom0_supported;
+	rte_xen_mem_phy2mch;
 
 } DPDK_2.1;