mac80211: correct use of IEEE80211_VHT_CAP_RXSTBC_X

The mod mask for VHT capabilities intends to say that you can override
the number of STBC receive streams, and it does, but only by accident.
The IEEE80211_VHT_CAP_RXSTBC_X aren't bits to be set, but values (albeit
left-shifted).  ORing the bits together gets the right answer, but we
should use the _MASK macro here instead.
Signed-off-by: Danek Duvall <duvall@comfychair.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -470,10 +470,7 @@ static const struct ieee80211_vht_cap mac80211_vht_capa_mod_mask = {
 		cpu_to_le32(IEEE80211_VHT_CAP_RXLDPC |
 			    IEEE80211_VHT_CAP_SHORT_GI_80 |
 			    IEEE80211_VHT_CAP_SHORT_GI_160 |
-			    IEEE80211_VHT_CAP_RXSTBC_1 |
-			    IEEE80211_VHT_CAP_RXSTBC_2 |
-			    IEEE80211_VHT_CAP_RXSTBC_3 |
-			    IEEE80211_VHT_CAP_RXSTBC_4 |
+			    IEEE80211_VHT_CAP_RXSTBC_MASK |
 			    IEEE80211_VHT_CAP_TXSTBC |
 			    IEEE80211_VHT_CAP_SU_BEAMFORMER_CAPABLE |
 			    IEEE80211_VHT_CAP_SU_BEAMFORMEE_CAPABLE |