i40e: Rewrite Flow Director busy wait loop

We can reorder the busy wait loop at the start of the Flow Director
transmit function to reduce the overall code size while still retaining the
same functionality.  As such I am taking advantage of the opportunity to do
so.

Change-ID: I34c403ca001953c6ac9816e65d5305e73d869026
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -122,7 +122,6 @@ static int i40e_program_fdir_filter(struct i40e_fdir_filter *fdir_data,
 	struct device *dev;
 	dma_addr_t dma;
 	u32 td_cmd = 0;
-	u16 delay = 0;
 	u16 i;
 
 	/* find existing FDIR VSI */
@@ -137,15 +136,11 @@ static int i40e_program_fdir_filter(struct i40e_fdir_filter *fdir_data,
 	dev = tx_ring->dev;
 
 	/* we need two descriptors to add/del a filter and we can wait */
-	do {
-		if (I40E_DESC_UNUSED(tx_ring) > 1)
-			break;
-		msleep_interruptible(1);
-		delay++;
-	} while (delay < I40E_FD_CLEAN_DELAY);
-
-	if (!(I40E_DESC_UNUSED(tx_ring) > 1))
+	for (i = I40E_FD_CLEAN_DELAY; I40E_DESC_UNUSED(tx_ring) < 2; i--) {
+		if (!i)
 			return -EAGAIN;
+		msleep_interruptible(1);
+	}
 
 	dma = dma_map_single(dev, raw_packet,
 			     I40E_FDIR_MAX_RAW_PACKET_SIZE, DMA_TO_DEVICE);