net: convert usage of packet_type to read_mostly

Protocols that use packet_type can be __read_mostly section for better
locality. Elminate any unnecessary initializations of NULL.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/block/aoe/aoenet.c b/drivers/block/aoe/aoenet.c
index c6099ba..ce0d62c 100644
--- a/drivers/block/aoe/aoenet.c
+++ b/drivers/block/aoe/aoenet.c
@@ -151,7 +151,7 @@
 	return 0;
 }
 
-static struct packet_type aoe_pt = {
+static struct packet_type aoe_pt __read_mostly = {
 	.type = __constant_htons(ETH_P_AOE),
 	.func = aoenet_rcv,
 };