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/omap3_ha_defconfig b/configs/omap3_ha_defconfig
index 3ef3f59..5f385c6 100644
--- a/configs/omap3_ha_defconfig
+++ b/configs/omap3_ha_defconfig
@@ -1,9 +1,9 @@
 CONFIG_ARM=y
 CONFIG_OMAP34XX=y
 CONFIG_TARGET_TAO3530=y
-CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="SYS_BOARD_OMAP3_HA"
 CONFIG_BOOTDELAY=3
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_IMLS is not set