x86: Add an option to control the position of SPL

For Apollo Lake SPL is run from CAR (cache-as-RAM) which is in a different
location from where SPL must be placed in ROM. In other words, although
SPL runs before SDRAM is set up, it is not execute-in-place (XIP).

Add a Kconfig option for the ROM position.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9d7ff3c..1d08cb2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -904,4 +904,9 @@
 	depends on HAVE_SYS_TEXT_BASE
 	default SYS_TEXT_BASE
 
+config X86_OFFSET_SPL
+	hex "Offset of SPL in ROM image"
+	depends on SPL && X86
+	default SPL_TEXT_BASE
+
 endmenu