arch/x86: Enable ebda library for romstage and postcar

This patch provides a kconfig option as EARLY_EBDA_INIT to
ensures user can make use of EBDA library even during early
boot stages like romstage, postcar.

Change-Id: I603800a531f56b6ebd460d5951c35a645fbfe492
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/21388
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/arch/x86/Kconfig

@@ -135,6 +135,15 @@ config PRERAM_CBMEM_CONSOLE_SIZE
 	help
 	  Increase this value if preram cbmem console is getting truncated
 
+config EARLY_EBDA_INIT
+	bool
+	default n
+	help
+	  Initialize BIOS EBDA area early in romstage to allow bootloader to
+	  use this region for storing data which can be available across
+	  various stages. If user is selecting this option then its users
+	  responsibility to perform EBDA initialization call during romstage.
+
 config PC80_SYSTEM
 	bool
 	default y if ARCH_X86