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/soc/intel/apollolake/Kconfig

@@ -24,6 +24,7 @@ config CPU_SPECIFIC_OPTIONS
 	select MMCONF_SUPPORT
 	select MMCONF_SUPPORT_DEFAULT
 	select NO_FIXED_XIP_ROM_SIZE
+	select NO_XIP_EARLY_STAGES
 	select PARALLEL_MP
 	select PCIEXP_ASPM
 	select PCIEXP_COMMON_CLOCK