dma: ipu: Drop unused spinlock

I was checking why this spinlock was never initialized, but it turns
out it's not used anywhere, so we can drop it.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: NDan Williams <djbw@fb.com>

drivers/dma/ipu/ipu_irq.c

@@ -44,7 +44,6 @@ static void ipu_write_reg(struct ipu *ipu, u32 value, unsigned long reg)
 struct ipu_irq_bank {
 	unsigned int	control;
 	unsigned int	status;
-	spinlock_t	lock;
 	struct ipu	*ipu;
 };