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/powerpc/cpu/ppc4xx/miiphy.c b/arch/powerpc/cpu/ppc4xx/miiphy.c
index 22ed5c2..4fec126 100644
--- a/arch/powerpc/cpu/ppc4xx/miiphy.c
+++ b/arch/powerpc/cpu/ppc4xx/miiphy.c
@@ -338,7 +338,7 @@
 	return 0;
 }
 
-int emac4xx_miiphy_read (char *devname, unsigned char addr, unsigned char reg,
+int emac4xx_miiphy_read (const char *devname, unsigned char addr, unsigned char reg,
 			 unsigned short *value)
 {
 	unsigned long sta_reg;
@@ -359,7 +359,7 @@
 /* write a phy reg and return the value with a rc	    */
 /***********************************************************/
 
-int emac4xx_miiphy_write (char *devname, unsigned char addr, unsigned char reg,
+int emac4xx_miiphy_write (const char *devname, unsigned char addr, unsigned char reg,
 			  unsigned short value)
 {
 	return emac_miiphy_command(addr, reg, EMAC_STACR_WRITE, value);