powerpc: ppc4xx: Move CANYONLANDS/GLACIER/ARCHES to Kconfig

Move these options to Kconfig and remove them from the CONFIG files.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/amcc/canyonlands/Kconfig b/board/amcc/canyonlands/Kconfig
index 530a6ef..0fc6877 100644
--- a/board/amcc/canyonlands/Kconfig
+++ b/board/amcc/canyonlands/Kconfig
@@ -9,4 +9,24 @@
 config SYS_CONFIG_NAME
 	default "canyonlands"
 
+choice BOARD_TYPE
+	prompt "Select which board to build for"
+
+config CANYONLANDS
+	bool "Glacier"
+	help
+	  Select this to build for the Canyonlands 460EX board.
+
+config GLACIER
+	bool "Glacier"
+	help
+	  Select this to build for the Glacier 460GT board.
+
+config ARCHES
+	bool "Arches"
+	help
+	  Select this to build for the Arches dual 460GT board.
+
+endchoice
+
 endif