Kconfig: Move SPL settings into their own file

Move the SPL settings into common/spl where most of the SPL code is kept.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/clearfog_defconfig b/configs/clearfog_defconfig
index 778cf06..d55ac64 100644
--- a/configs/clearfog_defconfig
+++ b/configs/clearfog_defconfig
@@ -2,8 +2,8 @@
 CONFIG_ARCH_MVEBU=y
 CONFIG_TARGET_CLEARFOG=y
 CONFIG_DEFAULT_DEVICE_TREE="armada-388-clearfog"
-CONFIG_SPL=y
 CONFIG_BOOTDELAY=3
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set