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/orangepi_plus_defconfig b/configs/orangepi_plus_defconfig
index f2ed941..031fcd0 100644
--- a/configs/orangepi_plus_defconfig
+++ b/configs/orangepi_plus_defconfig
@@ -8,8 +8,8 @@
 CONFIG_USB1_VBUS_PIN="PG13"
 CONFIG_DEFAULT_DEVICE_TREE="sun8i-h3-orangepi-plus"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
-CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="SATAPWR=SUNXI_GPG(11),MACPWR=SUNXI_GPD(6)"
+CONFIG_SPL=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set