cfg80211: use enum nl80211_dfs_regions for dfs_region everywhere

u8 was used in some other places, just stick to the enum,
this forces us to express the values that are expected.

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/reg.h b/net/wireless/reg.h
index b4076ba..cc4c2c0 100644
--- a/net/wireless/reg.h
+++ b/net/wireless/reg.h
@@ -20,7 +20,7 @@
 
 bool reg_is_valid_request(const char *alpha2);
 bool is_world_regdom(const char *alpha2);
-bool reg_supported_dfs_region(u8 dfs_region);
+bool reg_supported_dfs_region(enum nl80211_dfs_regions dfs_region);
 
 int regulatory_hint_user(const char *alpha2,
 			 enum nl80211_user_reg_hint_type user_reg_hint_type);