vhost: fix error handling for memory region alloc

callers of vhost_kvzalloc() expect the same behaviour on
allocation error as from kmalloc/vmalloc i.e. NULL return
value. So just return vzmalloc() returned value instead of
returning ERR_PTR(-ENOMEM)

Fixes: 4de7255f7d2be5 ("vhost: extend memory regions allocation to vmalloc")

Spotted-by: Dan Carpenter <[e-mail]>
Suggested-by: Julia Lawall <[e-mail]>
Signed-off-by: Igor Mammedov <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/vhost/vhost.c

···
 {
 	void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
 
-	if (!n) {
+	if (!n)
 		n = vzalloc(size);
-		if (!n)
-			return ERR_PTR(-ENOMEM);
-	}
 	return n;
 }