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: NSudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Acked-by: NChunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>