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/da850evm_defconfig b/configs/da850evm_defconfig
index da6615f..5953785 100644
--- a/configs/da850evm_defconfig
+++ b/configs/da850evm_defconfig
@@ -1,10 +1,10 @@
 CONFIG_ARM=y
 CONFIG_ARCH_DAVINCI=y
 CONFIG_TARGET_DA850EVM=y
-CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="MAC_ADDR_IN_SPIFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot > "
 CONFIG_CMD_BOOTZ=y