[TG3]: Add TSO workaround using GSO

Use GSO to workaround a rare TSO bug on some chips.  This hardware
bug may be triggered when the TSO header size is greater than 80
bytes.  When this condition is detected in a TSO packet, the driver
will use GSO to segment the packet to workaround the hardware bug.

Thanks to Juergen Kreileder <jk@blackdown.de> for reporting the
problem and collecting traces to help debug the problem.

And thanks to Herbert Xu <herbert@gondor.apana.org.au> for providing
the GSO mechanism that happens to be the perfect workaround for this
problem.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 97a8604..ba2c987 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -125,6 +125,7 @@
 #define  CHIPREV_ID_5750_A0		 0x4000
 #define  CHIPREV_ID_5750_A1		 0x4001
 #define  CHIPREV_ID_5750_A3		 0x4003
+#define  CHIPREV_ID_5750_C2		 0x4202
 #define  CHIPREV_ID_5752_A0_HW		 0x5000
 #define  CHIPREV_ID_5752_A0		 0x6000
 #define  CHIPREV_ID_5752_A1		 0x6001
@@ -2193,7 +2194,7 @@
 #define TG3_FLAG_INIT_COMPLETE		0x80000000
 	u32				tg3_flags2;
 #define TG3_FLG2_RESTART_TIMER		0x00000001
-/*					0x00000002 available */
+#define TG3_FLG2_HW_TSO_1_BUG		0x00000002
 #define TG3_FLG2_NO_ETH_WIRE_SPEED	0x00000004
 #define TG3_FLG2_IS_5788		0x00000008
 #define TG3_FLG2_MAX_RXPEND_64		0x00000010