usb: mtu3: declare functions static

The only user of the  functions mtu3_irq() and gpd_ring_empty() are in
the same file. They can be declared as static.
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Acked-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/mtu3/mtu3_core.c

@@ -696,7 +696,7 @@ static irqreturn_t mtu3_u2_common_isr(struct mtu3 *mtu)
 	return IRQ_HANDLED;
 }
 
-irqreturn_t mtu3_irq(int irq, void *data)
+static irqreturn_t mtu3_irq(int irq, void *data)
 {
 	struct mtu3 *mtu = (struct mtu3 *)data;
 	unsigned long flags;

drivers/usb/mtu3/mtu3_qmu.c

@@ -168,7 +168,7 @@ static struct qmu_gpd *advance_deq_gpd(struct mtu3_gpd_ring *ring)
 }
 
 /* check if a ring is emtpy */
-int gpd_ring_empty(struct mtu3_gpd_ring *ring)
+static int gpd_ring_empty(struct mtu3_gpd_ring *ring)
 {
 	struct qmu_gpd *enq = ring->enqueue;
 	struct qmu_gpd *next;