firewire: restore the device.h include in linux/firewire.h

Commit 313162d0 ("device.h: audit and cleanup users in main include
dir") exchanged an include <linux/device.h> for a struct *device but in
actuality I misread this file when creating 313162d0 and it should have
remained an include.

There were no build regressions since all consumers were already getting
device.h anyway, but make it right regardless.
Reported-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/firewire.h

@@ -2,6 +2,7 @@
 #define _LINUX_FIREWIRE_H
 
 #include <linux/completion.h>
+#include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
@@ -64,8 +65,6 @@
 #define CSR_MODEL		0x17
 #define CSR_DIRECTORY_ID	0x20
 
-struct device;
-
 struct fw_csr_iterator {
 	const u32 *p;
 	const u32 *end;