ixbge: fix bug when using large pages and jumbo frames

it was pointed out on the list that ixgbe was failing when using 64kB pages
and large 16kB MTU.

since with a 64kB PAGE_SIZE MAX_SKB_FRAGS = 3, the way the driver was
configuring page usage was assuming 2kB is half a page, and was only
ever dmaing that much data to a half page.

(16kB - header size) / 2048 = 7 or 8 pages, which would far exceed 3

adjust the driver to account for these large pages, the hardware can
support DMA to up to 16kB for each descriptor.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ixgbe/ixgbe.h b/drivers/net/ixgbe/ixgbe.h
index c0e56aa..2d877da 100644
--- a/drivers/net/ixgbe/ixgbe.h
+++ b/drivers/net/ixgbe/ixgbe.h
@@ -71,6 +71,7 @@
 #define IXGBE_RXBUFFER_128   128    /* Used for packet split */
 #define IXGBE_RXBUFFER_256   256    /* Used for packet split */
 #define IXGBE_RXBUFFER_2048  2048
+#define IXGBE_MAX_RXBUFFER   16384  /* largest size for a single descriptor */
 
 #define IXGBE_RX_HDR_SIZE IXGBE_RXBUFFER_256