rtlwifi: rtl8192c-common: Fix "BUG: KASAN:

rtlwifi: rtl8192c-common: Fix "BUG: KASAN:

Kernels built with CONFIG_KASAN=y report the following BUG for rtl8192cu
and rtl8192c-common:

==================================================================
BUG: KASAN: slab-out-of-bounds in rtl92c_dm_bt_coexist+0x858/0x1e40
     [rtl8192c_common] at addr ffff8801c90edb08
Read of size 1 by task kworker/0:1/38
page:ffffea0007243800 count:1 mapcount:0 mapping:          (null)
     index:0x0 compound_mapcount: 0
flags: 0x8000000000004000(head)
page dumped because: kasan: bad access detected
CPU: 0 PID: 38 Comm: kworker/0:1 Not tainted 4.9.7-gentoo #3
Hardware name: Gigabyte Technology Co., Ltd. To be filled by
     O.E.M./Z77-DS3H, BIOS F11a 11/13/2013
Workqueue: rtl92c_usb rtl_watchdog_wq_callback [rtlwifi]
  0000000000000000 ffffffff829eea33 ffff8801d7f0fa30 ffff8801c90edb08
  ffffffff824c0f09 ffff8801d4abee80 0000000000000004 0000000000000297
  ffffffffc070b57c ffff8801c7aa7c48 ffff880100000004 ffffffff000003e8
Call Trace:
  [<ffffffff829eea33>] ? dump_stack+0x5c/0x79
  [<ffffffff824c0f09>] ? kasan_report_error+0x4b9/0x4e0
  [<ffffffffc070b57c>] ? _usb_read_sync+0x15c/0x280 [rtl_usb]
  [<ffffffff824c0f75>] ? __asan_report_load1_noabort+0x45/0x50
  [<ffffffffc06d7a88>] ? rtl92c_dm_bt_coexist+0x858/0x1e40 [rtl8192c_common]
  [<ffffffffc06d7a88>] ? rtl92c_dm_bt_coexist+0x858/0x1e40 [rtl8192c_common]
  [<ffffffffc06d0cbe>] ? rtl92c_dm_rf_saving+0x96e/0x1330 [rtl8192c_common]
...

The problem is due to rtl8192ce and rtl8192cu sharing routines, and having
different layouts of struct rtl_pci_priv, which is used by rtl8192ce, and
struct rtl_usb_priv, which is used by rtl8192cu. The problem was resolved
by placing the struct bt_coexist_info at the head of each of those private
areas.

Reported-and-tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org> # 4.0+
Cc: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>