cfg80211: make device_type const

Instances of struct device_type are never modified, make them const.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 484facf..99b0cad 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -91,7 +91,7 @@
 /* To trigger userspace events */
 static struct platform_device *reg_pdev;
 
-static struct device_type reg_device_type = {
+static const struct device_type reg_device_type = {
 	.uevent = reg_device_uevent,
 };