cfg80211: fix MFP bug, sparse warnings

sparse warns about a number of things, and one of them
(use_mfp shadowed variable) actually is a bug, fix all
of them.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index df22048..4976eac 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -3239,11 +3239,11 @@
 	}
 
 	if (info->attrs[NL80211_ATTR_USE_MFP]) {
-		enum nl80211_mfp use_mfp =
+		enum nl80211_mfp mfp =
 			nla_get_u32(info->attrs[NL80211_ATTR_USE_MFP]);
-		if (use_mfp == NL80211_MFP_REQUIRED)
+		if (mfp == NL80211_MFP_REQUIRED)
 			use_mfp = true;
-		else if (use_mfp != NL80211_MFP_NO) {
+		else if (mfp != NL80211_MFP_NO) {
 			err = -EINVAL;
 			goto out;
 		}