net: use 32-bit arithmetic while allocating net device

Private part of allocation is never big enough to warrant size_t.

Space savings:

	add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
	function                                     old     new   delta
	alloc_netdev_mqs                            1120    1110     -10
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -7989,7 +7989,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 		unsigned int txqs, unsigned int rxqs)
 {
 	struct net_device *dev;
-	size_t alloc_size;
+	unsigned int alloc_size;
 	struct net_device *p;
 
 	BUG_ON(strlen(name) >= sizeof(dev->name));