rt2x00: conf_tx() only need register access for WMM queues

conf_tx() in rt61pci and rt73usb only have to check once
if the queue_idx indicates a non-WMM queue and break of
the function immediately if that is the case.

Only the WMM queues need to have the TX configuration written
to the registers.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt73usb.c b/drivers/net/wireless/rt2x00/rt73usb.c
index 961f9f93..60c43c1 100644
--- a/drivers/net/wireless/rt2x00/rt73usb.c
+++ b/drivers/net/wireless/rt2x00/rt73usb.c
@@ -2180,6 +2180,7 @@
 	struct rt2x00_field32 field;
 	int retval;
 	u32 reg;
+	u32 offset;
 
 	/*
 	 * First pass the configuration through rt2x00lib, that will
@@ -2191,24 +2192,23 @@
 	if (retval)
 		return retval;
 
+	/*
+	 * We only need to perform additional register initialization
+	 * for WMM queues/
+	 */
+	if (queue_idx >= 4)
+		return 0;
+
 	queue = rt2x00queue_get_queue(rt2x00dev, queue_idx);
 
 	/* Update WMM TXOP register */
-	if (queue_idx < 2) {
-		field.bit_offset = queue_idx * 16;
-		field.bit_mask = 0xffff << field.bit_offset;
+	offset = AC_TXOP_CSR0 + (sizeof(u32) * (!!(queue_idx & 2)));
+	field.bit_offset = (queue_idx & 1) * 16;
+	field.bit_mask = 0xffff << field.bit_offset;
 
-		rt2x00usb_register_read(rt2x00dev, AC_TXOP_CSR0, &reg);
-		rt2x00_set_field32(&reg, field, queue->txop);
-		rt2x00usb_register_write(rt2x00dev, AC_TXOP_CSR0, reg);
-	} else if (queue_idx < 4) {
-		field.bit_offset = (queue_idx - 2) * 16;
-		field.bit_mask = 0xffff << field.bit_offset;
-
-		rt2x00usb_register_read(rt2x00dev, AC_TXOP_CSR1, &reg);
-		rt2x00_set_field32(&reg, field, queue->txop);
-		rt2x00usb_register_write(rt2x00dev, AC_TXOP_CSR1, reg);
-	}
+	rt2x00usb_register_read(rt2x00dev, offset, &reg);
+	rt2x00_set_field32(&reg, field, queue->txop);
+	rt2x00usb_register_write(rt2x00dev, offset, reg);
 
 	/* Update WMM registers */
 	field.bit_offset = queue_idx * 4;