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/da850_am18xxevm_defconfig b/configs/da850_am18xxevm_defconfig
index ce49340..5b15c26 100644
--- a/configs/da850_am18xxevm_defconfig
+++ b/configs/da850_am18xxevm_defconfig
@@ -1,10 +1,10 @@
 CONFIG_ARM=y
 CONFIG_ARCH_DAVINCI=y
 CONFIG_TARGET_DA850EVM=y
-CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="DA850_AM18X_EVM,MAC_ADDR_IN_EEPROM,SYS_I2C_EEPROM_ADDR_LEN=2,SYS_I2C_EEPROM_ADDR=0x50"
 CONFIG_BOOTDELAY=3
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMLS is not set
 CONFIG_CMD_ASKENV=y