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/P2020RDB-PC_SPIFLASH_defconfig b/configs/P2020RDB-PC_SPIFLASH_defconfig
index 36c6c7e..9155768 100644
--- a/configs/P2020RDB-PC_SPIFLASH_defconfig
+++ b/configs/P2020RDB-PC_SPIFLASH_defconfig
@@ -19,6 +19,7 @@
 CONFIG_ENABLE_36BIT_PHYS=y
 CONFIG_SYS_MPC85XX_NO_RESETVEC=y
 CONFIG_SPL_SYS_MPC85XX_NO_RESETVEC=y
+CONFIG_USE_UBOOTPATH=y
 CONFIG_PCIE1=y
 CONFIG_PCIE2=y
 CONFIG_SYS_MONITOR_LEN=786432
@@ -77,6 +78,8 @@
 CONFIG_BOOTFILE="uImage"
 CONFIG_USE_ETHPRIME=y
 CONFIG_ETHPRIME="eTSEC1"
+CONFIG_USE_HOSTNAME=y
+CONFIG_USE_ROOTPATH=y
 CONFIG_LBA48=y
 CONFIG_DDR_CLK_FREQ=66666666
 CONFIG_SYS_SPD_BUS_NUM=1