wireless: max MSDU size for DMG networks

In the 802.11ad, aka DMG (Dynamic Multi-Gigabit), aka 60Ghz
spec, maximum MSDU size extended to 7920 bytes.
add #define for this.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/linux/ieee80211.h

@@ -154,6 +154,10 @@ static inline u16 ieee80211_sn_sub(u16 sn1, u16 sn2)
    802.11e clarifies the figure in section 7.1.2. The frame body is
    up to 2304 octets long (maximum MSDU size) plus any crypt overhead. */
 #define IEEE80211_MAX_DATA_LEN		2304
+/* 802.11ad extends maximum MSDU size for DMG (freq > 40Ghz) networks
+ * to 7920 bytes, see 8.2.3 General frame format
+ */
+#define IEEE80211_MAX_DATA_LEN_DMG	7920
 /* 30 byte 4 addr hdr, 2 byte QoS, 2304 byte MSDU, 12 byte crypt, 4 byte FCS */
 #define IEEE80211_MAX_FRAME_LEN		2352