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/configs/canyonlands_defconfig b/configs/canyonlands_defconfig
index 09b9ab9..37a2b4d 100644
--- a/configs/canyonlands_defconfig
+++ b/configs/canyonlands_defconfig
@@ -1,4 +1,4 @@
-CONFIG_SYS_EXTRA_OPTIONS="CANYONLANDS"
 CONFIG_PPC=y
 CONFIG_4xx=y
 CONFIG_TARGET_CANYONLANDS=y
+CONFIG_CANYONLANDS=y