e1000e: Use marco instead of digit for defining e1000_rx_desc_packet_split

In structure e1000_rx_desc_packet_split, the size of wb.upper.length is
defined by a digit. This may introduce some problem when the length is
changed.

This patch use the macro PS_PAGE_BUFFERS for the definition. And move the
definition to hw.h.
Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/e1000.h

@@ -90,9 +90,6 @@ struct e1000_info;
 
 #define E1000_MNG_VLAN_NONE		(-1)
 
-/* Number of packet split data buffers (not including the header buffer) */
-#define PS_PAGE_BUFFERS			(MAX_PS_BUFFERS - 1)
-
 #define DEFAULT_JUMBO			9234
 
 /* Time to wait before putting the device into D3 if there's no link (in ms). */

drivers/net/ethernet/intel/e1000e/hw.h

@@ -227,6 +227,9 @@ union e1000_rx_desc_extended {
 };
 
 #define MAX_PS_BUFFERS 4
+
+/* Number of packet split data buffers (not including the header buffer) */
+#define PS_PAGE_BUFFERS			(MAX_PS_BUFFERS - 1)
 /* Receive Descriptor - Packet Split */
 union e1000_rx_desc_packet_split {
 	struct {
@@ -251,7 +254,8 @@ union e1000_rx_desc_packet_split {
 		} middle;
 		struct {
 			__le16 header_status;
-			__le16 length[3];	/* length of buffers 1-3 */
+			/* length of buffers 1-3 */
+			__le16 length[PS_PAGE_BUFFERS];
 		} upper;
 		__le64 reserved;
 	} wb; /* writeback */