halbtc_send_bt_mp_operation() uses in_interrupt() to determine if it is
safe to invoke wait_for_completion().

The usage of in_interrupt() in drivers is phased out and Linus clearly
requested that code which changes behaviour depending on context should
either be separated or the context be conveyed in an argument passed by the
caller, which usually knows the context.

Aside of that in_interrupt() is not correct as it does not catch preempt
disabled regions which neither can sleep.

halbtc_send_bt_mp_operation() is called from:

 rtl_watchdog_wq_callback()
   rtl_btc_periodical()
     halbtc_get()
       case BTC_GET_U4_BT_PATCH_VER:
         halbtc_get_bt_patch_version()

 which is preemtible context.

   rtl_c2h_content_parsing()
     btc_ops->btc_btinfo_notify()
       rtl_btc_btinfo_notify()
         exhalbtc_bt_info_notify()
           ex_btc8723b1ant_bt_info_notify()
	   ex_btc8821a1ant_bt_info_notify()
	   ex_btc8821a2ant_bt_info_notify()
             btcoexist->btc_set_bt_reg()
               halbtc_set_bt_reg()

   rtl_c2h_content_parsing() is in turn called from:

   rtl_c2hcmd_wq_callback()
     rtl_c2hcmd_launcher()

   which is preemptible context and from:

   _rtl_pci_rx_interrupt
     rtl_c2hcmd_enqueue()

   which is obviously not preemptible but limited to C2H_BT_MP commands
   which does invoke rtl_c2h_content_parsing().

Aside of that it can be reached from:

     halbtc_get()
       case BTC_GET_U4_SUPPORTED_FEATURE:
         halbtc_get_bt_coex_supported_feature()
       case BTC_GET_U4_BT_FORBIDDEN_SLOT_VAL:
         halbtc_get_bt_forbidden_slot_val()
       case BTC_GET_U4_BT_DEVICE_INFO:
         halbtc_get_bt_device_info()
       case BTC_GET_U4_SUPPORTED_VERSION:
         halbtc_get_bt_coex_supported_version()
       case BTC_GET_U4_SUPPORTED_FEATURE:
         halbtc_get_bt_coex_supported_feature()

   btcoexist->btc_get_bt_afh_map_from_bt()
     halbtc_get_bt_afh_map_from_bt()

   btcoexist->btc_get_ble_scan_para_from_bt()
     halbtc_get_ble_scan_para_from_bt()

   btcoexist->btc_get_ble_scan_type_from_bt()
     halbtc_get_ble_scan_type_from_bt()

   btcoexist->btc_get_ant_det_val_from_bt()
     halbtc_get_ant_det_val_from_bt()

   btcoexist->btc_get_bt_coex_supported_version()
     halbtc_get_bt_coex_supported_version()

   btcoexist->btc_get_bt_coex_supported_feature()
     halbtc_get_bt_coex_supported_feature()

None of these have a caller. Welcome to the wonderful world of HALs and
onion layers.

Remove in_interrupt() check.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201101211536.2966644-9-bigeasy@linutronix.de