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/P1010RDB.h b/include/configs/P1010RDB.h
index f79c62a..d83563d 100644
--- a/include/configs/P1010RDB.h
+++ b/include/configs/P1010RDB.h
@@ -380,13 +380,10 @@
  * Environment Configuration
  */
 
-#define CONFIG_ROOTPATH		"/opt/nfsroot"
-#define CONFIG_UBOOTPATH	u-boot.bin/* U-Boot image on TFTP server */
-
 #define	CONFIG_EXTRA_ENV_SETTINGS				\
 	"hwconfig=" __stringify(CONFIG_DEF_HWCONFIG)  "\0"	\
 	"netdev=eth0\0"						\
-	"uboot=" __stringify(CONFIG_UBOOTPATH) "\0"		\
+	"uboot=" CONFIG_UBOOTPATH "\0"		\
 	"loadaddr=1000000\0"			\
 	"consoledev=ttyS0\0"				\
 	"ramdiskaddr=2000000\0"			\