staging: rtl8192u: Do not use GFP_KERNEL in atomic context

'rtl8192_irq_rx_tasklet()' is a tasklet initialized in
'rtl8192_init_priv_task()'.
>From this function it is possible to allocate some memory with the
GFP_KERNEL flag, which is not allowed in the atomic context of a tasklet.

Use GFP_ATOMIC instead.

The call chain is:
  rtl8192_irq_rx_tasklet            (in r8192U_core.c)
    --> rtl8192_rx_nomal            (in r8192U_core.c)
      --> ieee80211_rx              (in ieee80211/ieee80211_rx.c)
        --> RxReorderIndicatePacket (in ieee80211/ieee80211_rx.c)

Fixes: 79a5ccd9 ("staging: rtl8192u: fix large frame size compiler warning")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20200813173458.758284-1-christophe.jaillet@wanadoo.frSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c

@@ -597,7 +597,7 @@ static void RxReorderIndicatePacket(struct ieee80211_device *ieee,
 
 	prxbIndicateArray = kmalloc_array(REORDER_WIN_SIZE,
 					  sizeof(struct ieee80211_rxb *),
-					  GFP_KERNEL);
+					  GFP_ATOMIC);
 	if (!prxbIndicateArray)
 		return;