net: change the env name to use const

As we don't modify the 'name' parameter, so change it to const.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

include/net.h

@@ -233,8 +233,8 @@ void eth_set_current(void);		/* set nterface to ethcur var */
 
 int eth_get_dev_index(void);		/* get the device index */
 void eth_parse_enetaddr(const char *addr, uchar *enetaddr);
-int eth_getenv_enetaddr(char *name, uchar *enetaddr);
-int eth_setenv_enetaddr(char *name, const uchar *enetaddr);
+int eth_getenv_enetaddr(const char *name, uchar *enetaddr);
+int eth_setenv_enetaddr(const char *name, const uchar *enetaddr);
 
 /*
  * Get the hardware address for an ethernet interface .

net/eth.c

@@ -31,13 +31,13 @@ void eth_parse_enetaddr(const char *addr, uchar *enetaddr)
 	}
 }
 
-int eth_getenv_enetaddr(char *name, uchar *enetaddr)
+int eth_getenv_enetaddr(const char *name, uchar *enetaddr)
 {
 	eth_parse_enetaddr(getenv(name), enetaddr);
 	return is_valid_ethaddr(enetaddr);
 }
 
-int eth_setenv_enetaddr(char *name, const uchar *enetaddr)
+int eth_setenv_enetaddr(const char *name, const uchar *enetaddr)
 {
 	char buf[20];