cpu/amd/mtrr.h: Drop excessive includes

Change-Id: Id404bdab1f2361f1e7d20f7ee72111971863dddf
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17736
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/amd/thatcher/acpi_tables.c

@@ -22,7 +22,6 @@
 #include <arch/ioapic.h>
 #include <device/pci.h>
 #include <device/pci_ids.h>
-#include <cpu/amd/mtrr.h>
 #include <cpu/amd/amdfam15.h>
 
 unsigned long acpi_fill_madt(unsigned long current)