x86: make LOAD_FROM_32_BIT visible for platforms

This option is useful not only for development, but for the platforms
where U-Boot is run from custom ROM bootloader. For example, Intel
Edison is that board.

Make this option visible that platforms can select it if needed.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 675b56f..5f9597b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -195,6 +195,14 @@
 	depends on X86_RESET_VECTOR
 	default 0xfffff800
 
+config X86_LOAD_FROM_32_BIT
+	bool "Boot from a 32-bit program"
+	help
+	  Define this to boot U-Boot from a 32-bit program which sets
+	  the GDT differently. This can be used to boot directly from
+	  any stage of coreboot, for example, bypassing the normal
+	  payload-loading feature.
+
 config BOARD_ROMSIZE_KB_512
 	bool
 config BOARD_ROMSIZE_KB_1024