soc/intel/common: Bring DISPLAY_MTRRS into the light

Initially, I wanted to move only the Kconfig DISPLAY_MTRRS into the
"Debug" menu. It turned out, though, that the code looks rather generic.
No need to hide it in soc/intel/.

To not bloat src/Kconfig up any further, start a new `Kconfig.debug`
hierarchy just for debug options.

If somebody wants to review the code if it's 100% generic, we could
even get rid of HAVE_DISPLAY_MTRRS.

Change-Id: Ibd0a64121bd6e4ab5d7fd835f3ac25d3f5011f24
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/29684
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/quark/bootblock/bootblock.c

@@ -15,10 +15,10 @@
  */
 #include <bootblock_common.h>
 #include <console/console.h>
+#include <cpu/x86/mtrr.h>
 #include <device/pci_def.h>
 #include <program_loading.h>
 #include <soc/iomap.h>
-#include <soc/intel/common/util.h>
 #include <soc/pci_devs.h>
 #include <soc/reg_access.h>
 
@@ -112,8 +112,7 @@ void bootblock_soc_init(void)
 	if (IS_ENABLED(CONFIG_ENABLE_DEBUG_LED_SOC_INIT_ENTRY))
 		light_sd_led();
 
-	/* Display the MTRRs */
-	soc_display_mtrrs();
+	display_mtrrs();
 }
 
 void platform_prog_run(struct prog *prog)