firewire: clean up includes

Include required headers which were only indirectly included.
Remove unused includes and an unused constant.

Signed-off-by: Stefan Richter <[email protected]>
diff --git a/drivers/firewire/fw-iso.c b/drivers/firewire/fw-iso.c
index 2baf100..0ff3e9c 100644
--- a/drivers/firewire/fw-iso.c
+++ b/drivers/firewire/fw-iso.c
@@ -28,6 +28,8 @@
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
 
+#include <asm/byteorder.h>
+
 #include "fw-topology.h"
 #include "fw-transaction.h"