nl80211: add missing attribute validation for channel switch

Add missing attribute validation for NL80211_ATTR_OPER_CLASS
to the netlink policy.

Fixes: 1057d35ede ("cfg80211: introduce TDLS channel switch commands")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20200303051058.4089398-4-kuba@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -565,6 +565,7 @@ const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 		NLA_POLICY_MAX(NLA_U8, IEEE80211_NUM_UPS - 1),
 	[NL80211_ATTR_ADMITTED_TIME] = { .type = NLA_U16 },
 	[NL80211_ATTR_SMPS_MODE] = { .type = NLA_U8 },
+	[NL80211_ATTR_OPER_CLASS] = { .type = NLA_U8 },
 	[NL80211_ATTR_MAC_MASK] = {
 		.type = NLA_EXACT_LEN_WARN,
 		.len = ETH_ALEN