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/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 0fc4ced..e0801c2 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -68,4 +68,16 @@
 source "arch/powerpc/cpu/mpc8xx/Kconfig"
 source "arch/powerpc/lib/Kconfig"
 
+config USE_UBOOTPATH
+	bool "Set a default 'uboot' value in the environment"
+	help
+	  Many default environment scripts will check the "uboot" variable
+	  to determine the name of the file to load via tftp that will then
+	  be written to flash.
+
+config UBOOTPATH
+	string "Value of the default 'uboot' value in the environment"
+	depends on USE_UBOOTPATH
+	default "u-boot.bin"
+
 endmenu