ieee1394: support for slow links or slow 1394b phy ports

Add support for the following types of hardware:
 + nodes that have a link speed < PHY speed
 + 1394b PHYs that are less than S800 capable
 + 1394b/1394a adapter cable between two 1394b PHYs
Also, S1600 and S3200 are now supported if IEEE1394_SPEED_MAX is raised.

A probing function is added to nodemgr's config ROM fetching routine
which adjusts the allowable speed if an access problem was encountered.
Pros and Cons of the approach:
 + minimum code footprint to support this less widely used hardware
 + nearly no overhead for unaffected hardware
 - ineffective before nodemgr began to read the ROM of affected nodes
 - ineffective if ieee1394 is loaded with disable_nodemgr=1
The speed map CSRs which are published to the bus are not touched by the
patch.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Hakan Ardo <hakan@debian.org>
Cc: Calculex <linux@calculex.com>
Cc: Robert J. Kosinski <robk@cmcherald.com>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>

drivers/ieee1394/hosts.h

@@ -30,12 +30,13 @@ struct hpsb_host {
 
 	unsigned char iso_listen_count[64];
 
-	int node_count; /* number of identified nodes on this bus */
-	int selfid_count; /* total number of SelfIDs received */
-	int nodes_active; /* number of nodes that are actually active */
+	int node_count;     /* number of identified nodes on this bus */
+	int selfid_count;   /* total number of SelfIDs received */
+	int nodes_active;   /* number of nodes with active link layer */
+	u8 speed[63];       /* speed between each node and local node */
 
-	nodeid_t node_id; /* node ID of this host */
-	nodeid_t irm_id; /* ID of this bus' isochronous resource manager */
+	nodeid_t node_id;   /* node ID of this host */
+	nodeid_t irm_id;    /* ID of this bus' isochronous resource manager */
 	nodeid_t busmgr_id; /* ID of this bus' bus manager */
 
 	/* this nodes state */