ieee1394: raw1394: arm functions slept in atomic context

Sleeping functions like copy_to_user were accessed inside spinlocks in
raw1394's arm_register, arm_unregister, arm_get_buf, arm_set_buf.
http://bugzilla.kernel.org/show_bug.cgi?id=7120

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Tested-by: David Trent <DTrent@piacton.com>
(cherry picked from e575953ec17c3f5c1e738847d2d16c241bb99783 commit)