miiphy: constify device name

The driver name does not need to be writable, so constify it.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/arch/m68k/include/asm/fec.h b/arch/m68k/include/asm/fec.h
index 49311e5..cecec59 100644
--- a/arch/m68k/include/asm/fec.h
+++ b/arch/m68k/include/asm/fec.h
@@ -357,9 +357,9 @@
 void __mii_init(void);
 uint mii_send(uint mii_cmd);
 int mii_discover_phy(struct eth_device *dev);
-int mcffec_miiphy_read(char *devname, unsigned char addr,
+int mcffec_miiphy_read(const char *devname, unsigned char addr,
 		       unsigned char reg, unsigned short *value);
-int mcffec_miiphy_write(char *devname, unsigned char addr,
+int mcffec_miiphy_write(const char *devname, unsigned char addr,
 			unsigned char reg, unsigned short value);
 #endif