wifi: mt76: mt7915: fix oops on non-dbdc mt7986

mt7915_band_config() sets band_idx = 1 on the main phy for mt7986
with MT7975_ONE_ADIE or MT7976_ONE_ADIE.

Commit 0335c03 ("wifi: mt76: fix race condition related to
checking tx queue fill status") introduced a dereference of the
phys array indirectly indexed by band_idx via wcid->phy_idx in
mt76_wcid_cleanup(). This caused the following Oops on affected
mt7986 devices:

 Unable to handle kernel read from unreadable memory at virtual address 0000000000000024
 Mem abort info:
   ESR = 0x0000000096000005
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
   FSC = 0x05: level 1 translation fault
 Data abort info:
   ISV = 0, ISS = 0x00000005
   CM = 0, WnR = 0
 user pgtable: 4k pages, 39-bit VAs, pgdp=0000000042545000
 [0000000000000024] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000
 Internal error: Oops: 0000000096000005 [#1] SMP
 Modules linked in: ... mt7915e mt76_connac_lib mt76 mac80211 cfg80211 ...
 CPU: 2 PID: 1631 Comm: hostapd Not tainted 5.15.150 #0
 Hardware name: ZyXEL EX5700 (Telenor) (DT)
 pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : mt76_wcid_cleanup+0x84/0x22c [mt76]
 lr : mt76_wcid_cleanup+0x64/0x22c [mt76]
 sp : ffffffc00a803700
 x29: ffffffc00a803700 x28: ffffff80008f7300 x27: ffffff80003f3c00
 x26: ffffff80000a7880 x25: ffffffc008c26e00 x24: 0000000000000001
 x23: ffffffc000a68114 x22: 0000000000000000 x21: ffffff8004172cc8
 x20: ffffffc00a803748 x19: ffffff8004152020 x18: 0000000000000000
 x17: 00000000000017c0 x16: ffffffc008ef5000 x15: 0000000000000be0
 x14: ffffff8004172e28 x13: ffffff8004172e28 x12: 0000000000000000
 x11: 0000000000000000 x10: ffffff8004172e30 x9 : ffffff8004172e28
 x8 : 0000000000000000 x7 : ffffff8004156020 x6 : 0000000000000000
 x5 : 0000000000000031 x4 : 0000000000000000 x3 : 0000000000000001
 x2 : 0000000000000000 x1 : ffffff80008f7300 x0 : 0000000000000024
 Call trace:
  mt76_wcid_cleanup+0x84/0x22c [mt76]
  __mt76_sta_remove+0x70/0xbc [mt76]
  mt76_sta_state+0x8c/0x1a4 [mt76]
  mt7915_eeprom_get_power_delta+0x11e4/0x23a0 [mt7915e]
  drv_sta_state+0x144/0x274 [mac80211]
  sta_info_move_state+0x1cc/0x2a4 [mac80211]
  sta_set_sinfo+0xaf8/0xc24 [mac80211]
  sta_info_destroy_addr_bss+0x4c/0x6c [mac80211]

  ieee80211_color_change_finish+0x1c08/0x1e70 [mac80211]
  cfg80211_check_station_change+0x1360/0x4710 [cfg80211]
  genl_family_rcv_msg_doit+0xb4/0x110
  genl_rcv_msg+0xd0/0x1bc
  netlink_rcv_skb+0x58/0x120
  genl_rcv+0x34/0x50
  netlink_unicast+0x1f0/0x2ec
  netlink_sendmsg+0x198/0x3d0
  ____sys_sendmsg+0x1b0/0x210
  ___sys_sendmsg+0x80/0xf0
  __sys_sendmsg+0x44/0xa0
  __arm64_sys_sendmsg+0x20/0x30
  invoke_syscall.constprop.0+0x4c/0xe0
  do_el0_svc+0x40/0xd0
  el0_svc+0x14/0x4c
  el0t_64_sync_handler+0x100/0x110
  el0t_64_sync+0x15c/0x160
 Code: d2800002 910092c0 52800023 f9800011 (885f7c01)
 ---[ end trace 7e42dd9a39ed2281 ]---

Fix by using mt76_dev_phy() which will map band_idx to the correct phy
for all hardware combinations.

Fixes: 0335c03 ("wifi: mt76: fix race condition related to checking tx queue fill status")
Link: openwrt/openwrt#14548
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Link: https://patch.msgid.link/20240713130010.516037-1-bjorn@mork.no
Signed-off-by: Felix Fietkau <nbd@nbd.name>

Author: bmork

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -1529,7 +1529,7 @@ EXPORT_SYMBOL_GPL(mt76_wcid_init);
 
 void mt76_wcid_cleanup(struct mt76_dev *dev, struct mt76_wcid *wcid)
 {
-	struct mt76_phy *phy = dev->phys[wcid->phy_idx];
+	struct mt76_phy *phy = mt76_dev_phy(dev, wcid->phy_idx);
 	struct ieee80211_hw *hw;
 	struct sk_buff_head list;
 	struct sk_buff *skb;