ixgbe: Convert IXGBE_DESC_UNUSED from macro to static inline function

This change is a minor cleanup that converts the IXGBE_DESC_UNUSED macro
into a static inline function just for the case of the code being a bit
cleaner.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
index b308571..f8a22eb 100644
--- a/drivers/net/ixgbe/ixgbe_main.c
+++ b/drivers/net/ixgbe/ixgbe_main.c
@@ -882,7 +882,7 @@
 
 #define TX_WAKE_THRESHOLD (DESC_NEEDED * 2)
 	if (unlikely(count && netif_carrier_ok(tx_ring->netdev) &&
-		     (IXGBE_DESC_UNUSED(tx_ring) >= TX_WAKE_THRESHOLD))) {
+		     (ixgbe_desc_unused(tx_ring) >= TX_WAKE_THRESHOLD))) {
 		/* Make sure that anybody stopping the queue after this
 		 * sees the new next_to_clean.
 		 */
@@ -1474,7 +1474,7 @@
 	}
 
 	rx_ring->next_to_clean = i;
-	cleaned_count = IXGBE_DESC_UNUSED(rx_ring);
+	cleaned_count = ixgbe_desc_unused(rx_ring);
 
 	if (cleaned_count)
 		ixgbe_alloc_rx_buffers(rx_ring, cleaned_count);
@@ -3126,7 +3126,7 @@
 	IXGBE_WRITE_REG(hw, IXGBE_RXDCTL(reg_idx), rxdctl);
 
 	ixgbe_rx_desc_queue_enable(adapter, ring);
-	ixgbe_alloc_rx_buffers(ring, IXGBE_DESC_UNUSED(ring));
+	ixgbe_alloc_rx_buffers(ring, ixgbe_desc_unused(ring));
 }
 
 static void ixgbe_setup_psrtype(struct ixgbe_adapter *adapter)
@@ -6817,7 +6817,7 @@
 
 	/* We need to check again in a case another CPU has just
 	 * made room available. */
-	if (likely(IXGBE_DESC_UNUSED(tx_ring) < size))
+	if (likely(ixgbe_desc_unused(tx_ring) < size))
 		return -EBUSY;
 
 	/* A reprieve! - use start_queue because it doesn't call schedule */
@@ -6828,7 +6828,7 @@
 
 static int ixgbe_maybe_stop_tx(struct ixgbe_ring *tx_ring, int size)
 {
-	if (likely(IXGBE_DESC_UNUSED(tx_ring) >= size))
+	if (likely(ixgbe_desc_unused(tx_ring) >= size))
 		return 0;
 	return __ixgbe_maybe_stop_tx(tx_ring, size);
 }