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>

env/Kconfig

@@ -866,6 +866,16 @@ config ETHPRIME
 	help
 	  The value to set the "ethprime" variable to.
 
+config USE_HOSTNAME
+	bool "Set a default 'hostname' value in the environment"
+	default y if X86
+
+config HOSTNAME
+	string "Value of the default 'hostname' value in the environment"
+	depends on USE_HOSTNAME
+	default "x86" if X86
+	default "unknown"
+
 config VERSION_VARIABLE
 	bool "Add a 'ver' environment variable with the U-Boot version"
 	help