gianfar: Use memset instead of cacheable_memzero

cacheable_memzero() is completely overkill for the clearing out the FCB
block which is only 8-bytes.  The compiler should easily optimize this
with memset.  Additionally, cacheable_memzero() only exists on ppc32 and
thus breaks builds of gianfar on ppc64.
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/gianfar.c

@@ -1207,7 +1207,8 @@ static int gfar_enet_open(struct net_device *dev)
 static inline struct txfcb *gfar_add_fcb(struct sk_buff *skb)
 {
 	struct txfcb *fcb = (struct txfcb *)skb_push(skb, GMAC_FCB_LEN);
-	cacheable_memzero(fcb, GMAC_FCB_LEN);
+
+	memset(fcb, 0, GMAC_FCB_LEN);
 
 	return fcb;
 }