[SCSI] fcoe: Fix preempt count leak in fcoe_filter_frames()

The error exit path leaks preempt count. Add the missing put_cpu().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Yi Zou <yi.zou@intel.com>
Cc: stable@kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>