ath9k: fix client mode beacon configuration

ath9k: fix client mode beacon configuration

For pure station mode, iter_data.primary_beacon_vif was used and passed
to ath_beacon_config, but not set to the station vif.
This was causing the following warning:

[  100.310919] ------------[ cut here ]------------
[  100.315683] WARNING: CPU: 0 PID: 7 at compat-wireless-2016-06-20/drivers/net/wireless/ath/ath9k/beacon.c:642 ath9k_calculate_summary_state+0x250/0x60c [ath9k]()
[  100.402028] CPU: 0 PID: 7 Comm: kworker/u2:1 Tainted: G        W       4.4.15 #5
[  100.409676] Workqueue: phy0 ieee80211_ibss_leave [mac80211]
[  100.415351] Stack : 8736e98c 870b4b20 87a25b54 800a6800 8782a080 80400d63 8039b96c 00000007
[  100.415351]    803c5edc 87875914 80400000 800a47cc 87a25b54 800a6800 803a0fd8 80400000
[  100.415351]    00000003 87875914 80400000 80094ae0 87a25b54 8787594c 00000000 801ef308
[  100.415351]    803ffe70 801ef300 87193d58 87b3a400 87b3ad00 70687930 00000000 00000000
[  100.415351]    00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[  100.415351]    ...
[  100.451703] Call Trace:
[  100.454235] [<800a6800>] vprintk_default+0x24/0x30
[  100.459110] [<800a47cc>] printk+0x2c/0x38
[  100.463190] [<800a6800>] vprintk_default+0x24/0x30
[  100.468072] [<80094ae0>] print_worker_info+0x148/0x174
[  100.473378] [<801ef308>] serial8250_console_putchar+0x0/0x44
[  100.479122] [<801ef300>] wait_for_xmitr+0xc4/0xcc
[  100.484014] [<87193d58>] ieee80211_ibss_leave+0xb90/0x1900 [mac80211]
[  100.490590] [<80081604>] warn_slowpath_common+0xa0/0xd0
[  100.495922] [<801a359c>] dump_stack+0x14/0x28
[  100.500350] [<80071a00>] show_stack+0x50/0x84
[  100.504784] [<80081604>] warn_slowpath_common+0xa0/0xd0
[  100.510106] [<87024c60>] ath9k_calculate_summary_state+0x250/0x60c [ath9k]
[  100.517105] [<800816b8>] warn_slowpath_null+0x18/0x24
[  100.522256] [<87024c60>] ath9k_calculate_summary_state+0x250/0x60c [ath9k]
[  100.529273] [<87025418>] ath9k_set_txpower+0x148/0x498 [ath9k]
[  100.535302] [<871d2c64>] cleanup_module+0xa74/0xd4c [mac80211]
[  100.541237] [<801ef308>] serial8250_console_putchar+0x0/0x44
[  100.547042] [<800a5d18>] wake_up_klogd+0x54/0x68
[  100.551730] [<800a6650>] vprintk_emit+0x404/0x43c
[  100.556623] [<871b9db8>] ieee80211_sta_rx_notify+0x258/0x32c [mac80211]
[  100.563475] [<871ba6a4>] ieee80211_sta_rx_queued_mgmt+0x63c/0x734 [mac80211]
[  100.570693] [<871aa49c>] ieee80211_tx_prepare_skb+0x210/0x230 [mac80211]
[  100.577609] [<800af5d4>] mod_timer+0x15c/0x190
[  100.582220] [<871ba8b8>] ieee80211_sta_work+0xfc/0xe1c [mac80211]
[  100.588539] [<871940b4>] ieee80211_ibss_leave+0xeec/0x1900 [mac80211]
[  100.595122] [<8009ec84>] dequeue_task_fair+0x44/0x130
[  100.600281] [<80092a34>] process_one_work+0x1f8/0x334
[  100.605454] [<80093830>] worker_thread+0x2b4/0x408
[  100.610317] [<8009357c>] worker_thread+0x0/0x408
[  100.615019] [<8009357c>] worker_thread+0x0/0x408
[  100.619705] [<80097b68>] kthread+0xdc/0xe8
[  100.623886] [<80097a8c>] kthread+0x0/0xe8
[  100.627961] [<80060878>] ret_from_kernel_thread+0x14/0x1c
[  100.633448]
[  100.634956] ---[ end trace aafbe57e9ae6862f ]---

Fixes: cfda2d8e2314 ("ath9k: Fix beacon configuration for addition/removal of interfaces")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>