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/microblaze-generic_defconfig b/configs/microblaze-generic_defconfig
index c184923..047fd60 100644
--- a/configs/microblaze-generic_defconfig
+++ b/configs/microblaze-generic_defconfig
@@ -6,11 +6,11 @@
 CONFIG_XILINX_MICROBLAZE0_USE_HW_MUL=1
 CONFIG_SYS_TEXT_BASE=0x29000000
 CONFIG_DEFAULT_DEVICE_TREE="microblaze-generic"
-CONFIG_SPL=y
-CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_BOOTDELAY=-1
+CONFIG_SPL=y
+CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot-mONStR> "
 CONFIG_CMD_ASKENV=y