make RTL8169_READ_GMII_REG, RTL8169_WRITE_GMII_REG static

src/drivers/net/r8169.c

 //      20-16   5-bit GMII/MII register address
 //      15-0    16-bit GMII/MII register data
 //=================================================================
-void RTL8169_WRITE_GMII_REG(unsigned long ioaddr, int RegAddr, int value)
+static void RTL8169_WRITE_GMII_REG(unsigned long ioaddr, int RegAddr, int value)
 {
 	int i;
 
 }
 
 //=================================================================
-int RTL8169_READ_GMII_REG(unsigned long ioaddr, int RegAddr)
+static int RTL8169_READ_GMII_REG(unsigned long ioaddr, int RegAddr)
 {
 	int i, value = -1;