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/configs/uniphier_v7_defconfig b/configs/uniphier_v7_defconfig
index e3087a9..765d42a 100644
--- a/configs/uniphier_v7_defconfig
+++ b/configs/uniphier_v7_defconfig
@@ -51,6 +51,16 @@
 CONFIG_USE_BOOTFILE=y
 CONFIG_BOOTFILE="zImage"
 CONFIG_NET_RANDOM_ETHADDR=y
+CONFIG_USE_GATEWAYIP=y
+CONFIG_GATEWAYIP="192.168.11.1"
+CONFIG_USE_IPADDR=y
+CONFIG_IPADDR="192.168.11.10"
+CONFIG_USE_NETMASK=y
+CONFIG_NETMASK="255.255.255.0"
+CONFIG_USE_ROOTPATH=y
+CONFIG_ROOTPATH="/nfs/root/path"
+CONFIG_USE_SERVERIP=y
+CONFIG_SERVERIP="192.168.11.1"
 CONFIG_GPIO_UNIPHIER=y
 CONFIG_MISC=y
 CONFIG_I2C_EEPROM=y