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>