rtl8712: replace printk with better solutions

Replace printk with netdev_printk helpers, dev_printk helpers or
pr_err/warn/info if there is no device info available.

Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/rtl8712/xmit_linux.c b/drivers/staging/rtl8712/xmit_linux.c
index 65542cb..4d22bb7 100644
--- a/drivers/staging/rtl8712/xmit_linux.c
+++ b/drivers/staging/rtl8712/xmit_linux.c
@@ -134,8 +134,7 @@
 	for (i = 0; i < 8; i++) {
 		pxmitbuf->pxmit_urb[i] = usb_alloc_urb(0, GFP_KERNEL);
 		if (pxmitbuf->pxmit_urb[i] == NULL) {
-			printk(KERN_ERR "r8712u: pxmitbuf->pxmit_urb[i]"
-			    " == NULL");
+			netdev_err(padapter->pnetdev, "pxmitbuf->pxmit_urb[i] == NULL\n");
 			return _FAIL;
 		}
 	}