system: move the rootfs skeleton choice

In the following commits, we'll be switching more options to be
conditional on the default or custom skeleton.

So, it makes sense that those options come after the choice of a
skeleton.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

system/Config.in

@@ -1,5 +1,33 @@
 menu "System configuration"
 
+choice
+	prompt "Root FS skeleton"
+
+config BR2_ROOTFS_SKELETON_DEFAULT
+	bool "default target skeleton"
+	help
+	  Use default target skeleton
+
+config BR2_ROOTFS_SKELETON_CUSTOM
+	bool "custom target skeleton"
+	help
+	  Use custom target skeleton.
+
+endchoice
+
+if BR2_ROOTFS_SKELETON_CUSTOM
+
+config BR2_ROOTFS_SKELETON_CUSTOM_PATH
+	string "custom target skeleton path"
+	help
+	  Path to custom target skeleton.
+
+# dummy config so merged /usr workarounds can also be activated for
+# custom rootfs skeleton
+config BR2_ROOTFS_MERGED_USR
+
+endif
+
 config BR2_TARGET_GENERIC_HOSTNAME
 	string "System hostname"
 	default "buildroot"
@@ -168,34 +196,6 @@ config BR2_ROOTFS_DEVICE_TABLE_SUPPORTS_EXTENDED_ATTRIBUTES
 	help
 	  Support extended attributes handling in device tables
 
-choice
-	prompt "Root FS skeleton"
-
-config BR2_ROOTFS_SKELETON_DEFAULT
-	bool "default target skeleton"
-	help
-	  Use default target skeleton
-
-config BR2_ROOTFS_SKELETON_CUSTOM
-	bool "custom target skeleton"
-	help
-	  Use custom target skeleton.
-
-endchoice
-
-if BR2_ROOTFS_SKELETON_CUSTOM
-
-config BR2_ROOTFS_SKELETON_CUSTOM_PATH
-	string "custom target skeleton path"
-	help
-	  Path to custom target skeleton.
-
-# dummy config so merged /usr workarounds can also be activated for
-# custom rootfs skeleton
-config BR2_ROOTFS_MERGED_USR
-
-endif
-
 if BR2_ROOTFS_SKELETON_DEFAULT
 
 config BR2_ROOTFS_MERGED_USR