nl80211: fix monitor flags

NLA_NESTED attributes cannot be empty, but we want to be able to
specify "no flags" (empty attribute) vs. "no change" (no attribute).
Therefore, remove the NLA_NESTED policy so it can work as an empty
attribute.

I guess I should have used a u32 for these flags instead, but we're
stuck with it now. Haven't noticed earlier because of a bug in iw...
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/nl80211.c

@@ -84,7 +84,7 @@ static struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] __read_mostly = {
 					       .len = NL80211_MAX_SUPP_RATES },
 	[NL80211_ATTR_STA_PLINK_ACTION] = { .type = NLA_U8 },
 	[NL80211_ATTR_STA_VLAN] = { .type = NLA_U32 },
-	[NL80211_ATTR_MNTR_FLAGS] = { .type = NLA_NESTED },
+	[NL80211_ATTR_MNTR_FLAGS] = { /* NLA_NESTED can't be empty */ },
 	[NL80211_ATTR_MESH_ID] = { .type = NLA_BINARY,
 				.len = IEEE80211_MAX_MESH_ID_LEN },
 	[NL80211_ATTR_MPATH_NEXT_HOP] = { .type = NLA_U32 },