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/igep0020_defconfig b/configs/igep0020_defconfig
index 992d48f..5105de7 100644
--- a/configs/igep0020_defconfig
+++ b/configs/igep0020_defconfig
@@ -1,10 +1,10 @@
 CONFIG_ARM=y
 CONFIG_OMAP34XX=y
 CONFIG_TARGET_OMAP3_IGEP00X0=y
-CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="MACH_TYPE=MACH_TYPE_IGEP0020"
 CONFIG_BOOTDELAY=3
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set