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/soc/intel/quark/include/soc/reg_access.h

@@ -5,7 +5,6 @@
 
 #include <cpu/x86/cr.h>
 #include <cpu/x86/msr.h>
-#include <cpu/x86/mtrr.h>
 #include <fsp/util.h>
 #include <reg_script.h>
 #include <soc/IntelQNCConfig.h>