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/am335x_shc_prompt_defconfig b/configs/am335x_shc_prompt_defconfig
index 764fc9f..f84020a 100644
--- a/configs/am335x_shc_prompt_defconfig
+++ b/configs/am335x_shc_prompt_defconfig
@@ -2,10 +2,10 @@
 CONFIG_TARGET_AM335X_SHC=y
 CONFIG_SERIES=y
 CONFIG_SPL_STACK_R_ADDR=0x82000000
-CONFIG_SPL=y
-CONFIG_SPL_STACK_R=y
 CONFIG_FIT=y
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
+CONFIG_SPL_STACK_R=y
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Enter 'shc' to enter prompt (times out) %d \nEnter 'noautoboot' to enter prompt without timeout\n"
 CONFIG_AUTOBOOT_DELAY_STR="shc"