vm: explicitly initialise kmalloc in vm_bootstrap

if kmalloc is called with count=N before vm_bootstrap is finished,
the request will be fulfilled using memblock_alloc.

if N is a power of 2, the returned pointer will be aligned to
an N-byte boundary.

vm/bootstrap.c

@@ -22,6 +22,7 @@ kern_status_t vm_bootstrap(const vm_zone_descriptor_t *zones, size_t nr_zones)
 		vm_zone_init(&node_data->pg_zones[zones[i].zd_id],  &zones[i]);
 	}
 
+	kmalloc_init();
 	return KERN_OK;
 }