src: Remove unused <cpu/x86/smm.h>

Change-Id: Ic3f85a8fbc6a84074f45d94514e1dcfa78cb0958
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50171
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/intel/baytrail/southcluster.c

@@ -7,7 +7,6 @@
 #include <acpi/acpi.h>
 #include <bootstate.h>
 #include <console/console.h>
-#include <cpu/x86/smm.h>
 #include <device/device.h>
 #include <device/pci.h>
 #include <device/pci_ids.h>