firewire: add CSR NODE_IDS support

The NODE_IDS register, and especially its bus_id field, is quite
useless because 1394.1 requires that the bus_id field always stays
0x3ff.  However, the 1394 specification requires this register on all
transaction capable nodes, and the Base 1394 Test Suite tests for it,
so we better implement it.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index c19e987..efcdeb2 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -76,6 +76,7 @@
 			       int node_id, int generation);
 
 	u32 (*read_csr_reg)(struct fw_card *card, int csr_offset);
+	void (*write_csr_reg)(struct fw_card *card, int csr_offset, u32 value);
 
 	struct fw_iso_context *
 	(*allocate_iso_context)(struct fw_card *card,