rtlwifi: usb: use usb_alloc_coherent for RX buffers

Use dedicated DMA coherent buffers for RX urbs, to avoid allocation of large
skbuffs in hard-irq context and improve performance.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rtlwifi/usb.h b/drivers/net/wireless/rtlwifi/usb.h
index fb986f9..22d7c68 100644
--- a/drivers/net/wireless/rtlwifi/usb.h
+++ b/drivers/net/wireless/rtlwifi/usb.h
@@ -141,6 +141,7 @@
 	u32 rx_max_size;	/* Bulk IN max buffer size */
 	u32 rx_urb_num;		/* How many Bulk INs are submitted to host. */
 	struct usb_anchor	rx_submitted;
+	struct usb_anchor	rx_cleanup_urbs;
 	void (*usb_rx_segregate_hdl)(struct ieee80211_hw *, struct sk_buff *,
 				     struct sk_buff_head *);
 	void (*usb_rx_hdl)(struct ieee80211_hw *, struct sk_buff *);