net: dsa: Make dsa_switch_ops const

Now that we have properly encapsulated and made drivers utilize exported
functions, we can switch dsa_switch_ops to be a annotated with const.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index 5202771..31d0170 100644
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -977,7 +977,7 @@ static struct b53_io_ops bcm_sf2_io_ops = {
 	.write64 = bcm_sf2_core_write64,
 };
 
-static struct dsa_switch_ops bcm_sf2_ops = {
+static const struct dsa_switch_ops bcm_sf2_ops = {
 	.get_tag_protocol	= bcm_sf2_sw_get_tag_protocol,
 	.setup			= bcm_sf2_sw_setup,
 	.get_strings		= b53_get_strings,