[POWERPC] fsl_soc: Make mac_addr const in fs_enet_of_init().

of_get_mac_address() returns a const pointer, so the result
should be stored in a const pointer.
Signed-off-by: NScott Wood <scottwood@freescale.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/sysdev/fsl_soc.c

@@ -907,7 +907,7 @@ static int __init fs_enet_of_init(void)
 		struct fs_platform_info fs_enet_data;
 		const unsigned int *id;
 		const unsigned int *phy_addr;
-		void *mac_addr;
+		const void *mac_addr;
 		const phandle *ph;
 		const char *model;