malloc: fix not unlocking hotplug on fail to init

We lock the hotplug during init, but do not unlock it if we couldn't
register multiprocess callbacks. Add the missing unlock.

Fixes: 07dcbfe0101f ("malloc: support multiprocess memory hotplug")

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

lib/librte_eal/common/malloc_heap.c

@@ -815,6 +815,7 @@ rte_eal_malloc_heap_init(void)
 
 	if (register_mp_requests()) {
 		RTE_LOG(ERR, EAL, "Couldn't register malloc multiprocess actions\n");
+		rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
 		return -1;
 	}