igb: add per-packet timestamping

This patch adds support for per-packet timestamping for the
82580 adapter. The rx timestamp code is also pulled out of the
inlined rx hotpath and instead moved to a seperate function.

This version adds a comment explaining the per-packet timestamping
code added to igb_hwtstamp_ioctl().

Signed-off-by: Nicholas Nunley <nicholasx.d.nunley@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/igb/igb.h b/drivers/net/igb/igb.h
index a177570..4f69b6d 100644
--- a/drivers/net/igb/igb.h
+++ b/drivers/net/igb/igb.h
@@ -107,6 +107,7 @@
 #define MAXIMUM_ETHERNET_VLAN_SIZE 1522
 
 /* Supported Rx Buffer Sizes */
+#define IGB_RXBUFFER_64    64     /* Used for packet split */
 #define IGB_RXBUFFER_128   128    /* Used for packet split */
 #define IGB_RXBUFFER_1024  1024
 #define IGB_RXBUFFER_2048  2048
@@ -324,6 +325,7 @@
 
 #define IGB_82576_TSYNC_SHIFT 19
 #define IGB_82580_TSYNC_SHIFT 24
+#define IGB_TS_HDR_LEN        16
 enum e1000_state_t {
 	__IGB_TESTING,
 	__IGB_RESETTING,