cpu/x86/mtrr: Get rid of CACHE_ROM_SIZE_OVERRIDE

As far as I can see this Kconfig option was used wrong ever since it
was added. According to the commit message of 107f72e (Re-declare
CACHE_ROM_SIZE as aligned ROM_SIZE for MTRR), it was only necessary
to prevent overlapping with CAR.

Let's handle the potential overlap in C macros instead and get rid
of that option. Currently, it was only used by most FSP1.0 boards,
and only because the `fsp1_0/Kconfig` set it to CBFS_SIZE (WTF?).

Change-Id: I4d0096f14a9d343c2e646e48175fe2127198a822
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/26566
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/drivers/intel/fsp1_0/Kconfig

@@ -103,15 +103,6 @@ config VIRTUAL_ROM_SIZE
 	  the SPI ROMs are loaded with an 8 MB coreboot image, the virtual ROM
 	  size is 16 MB.
 
-config CACHE_ROM_SIZE_OVERRIDE
-	hex "Cache ROM Size"
-	default CBFS_SIZE
-	help
-	  This is the size of the cachable area that is passed into the FSP in
-	  the early initialization.  Typically this should be the size of the CBFS
-	  area, but the size must be a power of 2 whereas the CBFS size does not
-	  have this limitation.
-
 config USE_GENERIC_FSP_CAR_INC
 	bool
 	default n