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/net/llc/llc_core.c b/net/llc/llc_core.c
index a7fe1ad..ff4c0ab 100644
--- a/net/llc/llc_core.c
+++ b/net/llc/llc_core.c
@@ -147,12 +147,12 @@
 	kfree(sap);
 }
 
-static struct packet_type llc_packet_type = {
+static struct packet_type llc_packet_type __read_mostly = {
 	.type = cpu_to_be16(ETH_P_802_2),
 	.func = llc_rcv,
 };
 
-static struct packet_type llc_tr_packet_type = {
+static struct packet_type llc_tr_packet_type __read_mostly = {
 	.type = cpu_to_be16(ETH_P_TR_802_2),
 	.func = llc_rcv,
 };