Remove CACHE_ROM.

With the recent improvement 3d6ffe76f8,
speedup by CACHE_ROM is reduced a lot.
On the other hand this makes coreboot run out of MTRRs depending on
system configuration, hence screwing up I/O access and cache
coherency in worst cases.

CACHE_ROM requires the user to sanity check their boot output because
the feature is brittle. The working configuration is dependent on I/O
hole size, ram size, and chipset. Because of this the current
implementation can leave a system configured in an inconsistent state
leading to unexpected results such as poor performance and/or
inconsistent cache-coherency

Remove this as a buggy feature until we figure out how to do it properly
if necessary.

Change-Id: I858d78a907bf042fcc21fdf7a2bf899e9f6b591d
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/5146
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/mainboard/intel/wtm2/Kconfig

@@ -13,7 +13,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select HAVE_ACPI_RESUME
 	select HAVE_SMI_HANDLER
 	select MAINBOARD_HAS_CHROMEOS
-	select CACHE_ROM
 	select MAINBOARD_HAS_NATIVE_VGA_INIT
 	select MONOTONIC_TIMER_MSR