rtl8188eu: Fix a possible sleep-in-atomic bug in rtw_disassoc_cmd

The driver may sleep under a spinlock, and the function call path is:
rtw_set_802_11_bssid(acquire the spinlock)
  rtw_disassoc_cmd
    kzalloc(GFP_KERNEL) --> may sleep

To fix it, GFP_KERNEL is replaced with GFP_ATOMIC.
This bug is found by my static analysis tool and my code review.
Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/core/rtw_cmd.c

@@ -508,7 +508,7 @@ u8 rtw_disassoc_cmd(struct adapter *padapter, u32 deauth_timeout_ms, bool enqueu
 
 	if (enqueue) {
 		/* need enqueue, prepare cmd_obj and enqueue */
-		cmdobj = kzalloc(sizeof(*cmdobj), GFP_KERNEL);
+		cmdobj = kzalloc(sizeof(*cmdobj), GFP_ATOMIC);
 		if (!cmdobj) {
 			res = _FAIL;
 			kfree(param);