[TG3]: Improve ASF heartbeat.

Change to a different ASF heartbeat message code to improve
reliability.

There were some reports of unintended resets on real time kernels
where the timer may be slow and cause the heartbeat to be late.
Netpoll will also have the same problem because the timer irq will
be unavailable.

Using the new heartbeat code, the ASF firmware will also check the
ring condition before resetting the chip when the heartbeat is
expiring.

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 f9c81ba..f7462c2 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -1537,6 +1537,7 @@
 #define  FWCMD_NICDRV_FIX_DMAR		 0x00000005
 #define  FWCMD_NICDRV_FIX_DMAW		 0x00000006
 #define  FWCMD_NICDRV_ALIVE2		 0x0000000d
+#define  FWCMD_NICDRV_ALIVE3		 0x0000000e
 #define NIC_SRAM_FW_CMD_LEN_MBOX	0x00000b7c
 #define NIC_SRAM_FW_CMD_DATA_MBOX	0x00000b80
 #define NIC_SRAM_FW_ASF_STATUS_MBOX	0x00000c00