mac80211: use CMAC_PN_LEN

Instead of hardcoding its value (6), use the constant.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/key.c

@@ -372,8 +372,9 @@ struct ieee80211_key *ieee80211_key_alloc(u32 cipher, int idx, size_t key_len,
 		key->conf.iv_len = 0;
 		key->conf.icv_len = sizeof(struct ieee80211_mmie);
 		if (seq)
-			for (j = 0; j < 6; j++)
-				key->u.aes_cmac.rx_pn[j] = seq[6 - j - 1];
+			for (j = 0; j < CMAC_PN_LEN; j++)
+				key->u.aes_cmac.rx_pn[j] =
+					seq[CMAC_PN_LEN - j - 1];
 		/*
 		 * Initialize AES key state here as an optimization so that
 		 * it does not need to be initialized for every packet.