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/T2080QDS_SPIFLASH_defconfig b/configs/T2080QDS_SPIFLASH_defconfig
index de35db3..8b4ebe3 100644
--- a/configs/T2080QDS_SPIFLASH_defconfig
+++ b/configs/T2080QDS_SPIFLASH_defconfig
@@ -1,13 +1,13 @@
 CONFIG_PPC=y
 CONFIG_MPC85xx=y
 CONFIG_TARGET_T208XQDS=y
-CONFIG_SPL=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_T2080,RAMBOOT_PBL,SPL_FSL_PBL,SPIFLASH"
 CONFIG_BOOTDELAY=10
+CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MMC=y