Convert CONFIG_HOSTNAME et al to Kconfig

This converts the following to Kconfig:
   CONFIG_GATEWAYIP
   CONFIG_HOSTNAME
   CONFIG_IPADDR
   CONFIG_NETMASK
   CONFIG_ROOTPATH
   CONFIG_SERVERIP
   CONFIG_UBOOTPATH

To do this, we introduce a CONFIG_USE_ form of each of the above and
change include/env_default.h to test for that to be set before setting a
value. Further, we don't want to stringify the IP address related values
as they are now properly strings via Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/MPC8548CDS.h b/include/configs/MPC8548CDS.h
index 34b876f..1f1eacd 100644
--- a/include/configs/MPC8548CDS.h
+++ b/include/configs/MPC8548CDS.h
@@ -298,20 +298,10 @@
  * Environment Configuration
  */
 
-#define CONFIG_IPADDR	 192.168.1.253
-
-#define CONFIG_HOSTNAME	 "unknown"
-#define CONFIG_ROOTPATH	 "/nfsroot"
-#define CONFIG_UBOOTPATH	8548cds/u-boot.bin	/* TFTP server */
-
-#define CONFIG_SERVERIP	 192.168.1.1
-#define CONFIG_GATEWAYIP 192.168.1.1
-#define CONFIG_NETMASK	 255.255.255.0
-
 #define	CONFIG_EXTRA_ENV_SETTINGS		\
 	"hwconfig=fsl_ddr:ecc=off\0"		\
 	"netdev=eth0\0"				\
-	"uboot=" __stringify(CONFIG_UBOOTPATH) "\0"	\
+	"uboot=" CONFIG_UBOOTPATH "\0"	\
 	"tftpflash=tftpboot $loadaddr $uboot; "	\
 		"protect off " __stringify(CONFIG_TEXT_BASE)	\
 			" +$filesize; "	\