src: Remove unused 'include <cpu/x86/mtrr.h>'

Change-Id: I3f08b9cc34582165785063580b3356135030f63e
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41782
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: David Guckian

src/northbridge/intel/x4x/raminit.c

@@ -4,7 +4,6 @@
 #include <cbmem.h>
 #include <cf9_reset.h>
 #include <console/console.h>
-#include <cpu/x86/mtrr.h>
 #include <arch/cpu.h>
 #if CONFIG(SOUTHBRIDGE_INTEL_I82801GX)
 #include <southbridge/intel/i82801gx/i82801gx.h> /* smbus_read_byte */