treewide: Convert CONFIG_HOSTNAME to a string option

CONFIG_HOSTNAME is defined as a "plain" preprocessor string, but every
use is couched by __stringify(...).

Hence, convert it to a proper string option.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/include/configs/tuxx1.h b/include/configs/tuxx1.h
index b63bdf1..bb1d1db 100644
--- a/include/configs/tuxx1.h
+++ b/include/configs/tuxx1.h
@@ -26,19 +26,19 @@
  */
 #if defined(CONFIG_KMSUPX5)
 #define CONFIG_KM_BOARD_NAME	"kmsupx5"
-#define CONFIG_HOSTNAME		kmsupx5
+#define CONFIG_HOSTNAME		"kmsupx5"
 #elif defined(CONFIG_TUGE1)
 #define CONFIG_KM_BOARD_NAME	"tuge1"
-#define CONFIG_HOSTNAME		tuge1
+#define CONFIG_HOSTNAME		"tuge1"
 #elif defined(CONFIG_TUXX1)	/* TUXX1 board (tuxa1/tuda1) specific */
 #define CONFIG_KM_BOARD_NAME	"tuxx1"
-#define CONFIG_HOSTNAME		tuxx1
+#define CONFIG_HOSTNAME		"tuxx1"
 #elif defined(CONFIG_KMOPTI2)
 #define CONFIG_KM_BOARD_NAME	"kmopti2"
-#define CONFIG_HOSTNAME		kmopti2
+#define CONFIG_HOSTNAME		"kmopti2"
 #elif defined(CONFIG_KMTEPR2)
 #define CONFIG_KM_BOARD_NAME    "kmtepr2"
-#define CONFIG_HOSTNAME         kmtepr2
+#define CONFIG_HOSTNAME         "kmtepr2"
 #else
 #error ("Board not supported")
 #endif