firewire: core: add CSR SPLIT_TIMEOUT support

Implement the SPLIT_TIMEOUT registers.  Besides being required by the
spec, this is desirable for some IIDC devices and necessary for many
audio devices to be able to increase the timeout from userspace.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 72e2b8a..cdf8213 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -89,6 +89,11 @@
 	struct list_head transaction_list;
 	unsigned long reset_jiffies;
 
+	u32 split_timeout_hi;
+	u32 split_timeout_lo;
+	unsigned int split_timeout_cycles;
+	unsigned int split_timeout_jiffies;
+
 	unsigned long long guid;
 	unsigned max_receive;
 	int link_speed;