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/peach-pit_defconfig b/configs/peach-pit_defconfig
index 9778341..3b73237 100644
--- a/configs/peach-pit_defconfig
+++ b/configs/peach-pit_defconfig
@@ -3,9 +3,9 @@
 CONFIG_ARCH_EXYNOS5=y
 CONFIG_TARGET_PEACH_PIT=y
 CONFIG_DEFAULT_DEVICE_TREE="exynos5420-peach-pit"
-CONFIG_SPL=y
 CONFIG_FIT=y
 CONFIG_FIT_BEST_MATCH=y
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Peach-Pit # "
 CONFIG_CMD_BOOTZ=y