xip: Do not pass --xip for early stages if CAR supports code execution

On modern x86 platforms like apollolake, pre-RAM stages verstage and
romstage run within the cache-as-ram region. Thus, we do not need to
pass in the --xip parameter to cbfstool while adding these
stages. Introduce a new Kconfig variable NO_XIP_EARLY_STAGES which is
default false for all x86 platforms. Apollolake selects this option
since it supports code execution with CAR.

Change-Id: I2848046472f40f09ce7fc230c258b0389851b2ea
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/14623
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/Kconfig

@@ -199,6 +199,14 @@ config INCLUDE_CONFIG_FILE
 	    config                         0x8d740    raw          3324
 	    (empty)                        0x8e480    null         3610440
 
+config NO_XIP_EARLY_STAGES
+	bool
+	default n if ARCH_X86
+	default y
+	help
+	  Identify if --xip parameter needs to be passed into cbfstool for early
+	  stages.
+
 config EARLY_CBMEM_INIT
 	def_bool !LATE_CBMEM_INIT